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Blocking unwanted calls

PostPosted: 11/02/2022
by wonderdollar

Is there a way to block unwanted or telemarketers call on Freephoneline.?

Now a days we receive more than 10 - 15 unwanted calls, where no one will talk or leave a voice mail message. Please advise if there is a way to STOP or BLOCK these unwanted calls.



Re: Blocking unwanted calls

PostPosted: 11/02/2022
by Liptonbrisk
Blocking calls with FPL is based entirely on the SIP device, SIP app, or phone that you're using. Many DECT 6 phone handsets do have a block number feature. There's also 3rd party devices that plug into a telephone line and claim to block calls. I don't know how well those work.

Blocked calls will drop immediately to FPL's voicemail system, typically (one exception is being able to route unwanted calls to another phone number with Obihai IP Phones or Obihai ATAs).
The OBi2xx PDF guide explains how to do this with Obihai devices: viewtopic.php?f=15&t=18805#p73839 (PDF is located at the bottom of the first post).

In the FPL desktop app, you can block calls, by selecting "Menu"-->"Blacklist", and entering the number you want to block.

Newer Grandstream ATAs mention a blacklist for incoming calls feature: ... _guide.pdf.
Also visit ... king/44167.
You would find that feature under the advanced settings section of the Grandstream ATA's web user interface.
The number you enter in the blacklist should look exactly as it does in your FPL call logs:

I'm not sure if you're still using a Grandstream HT-287, which (but I'm completely guessing since I don't have access to one) probably lacks a blacklist feature.
I don't see the option to block calls in the HT-286 manual: ... _guide.pdf.

For Linksys/Cisco ATAs, visit viewtopic.php?f=14&t=2337&p=14070.

These methods (matching a specific number to block) aren't effective against scammers that spoof or fake random outbound caller ID phone numbers. However, you can create a whitelist with Obihai ATAs, which works as long as the scammer doesn't spoof one of the whitelisted numbers.

Lastly, don't answer calls from numbers you don't recognize. If the call is important enough, a voicemail will be left, and if it's not and you answer, the caller knows there's someone willing to engage in cold calls (non-leads). As a result, your FPL number will just get added to more telemarketing distribution lists.

Re: Blocking unwanted calls

PostPosted: 11/02/2022
by Liptonbrisk
If calls or ringing correspond with different numbers (that clearly aren't normal phone numbers) on your call display, such as 100, 1000, 1001, 9999, etc., those aren't calls and won't ever be listed in FPL call logs after logging in at If you pick up, you won't hear anything. They're SIP scanners. SIP scanners are programs written by crackers (script kiddies) or hackers. They look for ways to break into your home network by scanning for open ports. Typically, they'll scan for common service ports to see if they're open, such as UDP 5060, 5061 and a few others (some scan for a lot more than that). If a port is open, they can access your ATA (and, potentially, other devices on your LAN). Your phones will ring with caller IDs appearing as 1001, 999, something else that's clearly not a regular phone number, etc. These crackers will try to make free calls using your services (or much worse). That's why it's important to have a good NAT firewall in a router protecting your ATA, computers, and other devices on your LAN (local area network) and to never port forward or use DMZ. Port forwarding is a security risk. Enabling DMZ is even worse. Refer to point A below.

Typically, for VoIP SIP services, especially for Freephoneline/Fongo, you want

A) a router that does not have a full cone NAT,

Visit ... -punching/.
Mango from the forums writes,
“Use a restricted cone NAT router, and do not use port forwarding or DMZ. Restricted cone NAT will only permit
inbound traffic from the service provider you're registered to. If you have a full cone NAT router, it will allow traffic
from any source. This is probably not what you intend.
If you have a Windows computer, you can test your router using the utility here:,22292023. To run it, use stun from a command prompt.”
Essentially, you download the file; extract the stun.exe file from within the zip file to an easily
accessible location; use an elevated command prompt (visit ... inistrator); change directory (cd) to the
directory or location where you extracted stun.exe (visit ... c-commands); and type “stun” without
the quotation marks followed by the enter/return button on your keyboard.
Asus routers, at the time of this writing, produce port restricted cone NAT routers, for example and are fine,
provided you’re using one with Asuswrt-Merlin, third party firmware installed.

B) a router that lets you disable SIP ALG if it's buggy,

To understand why SIP ALG often causes horrible problems, please visit (scroll down to the section on SIP ALG problems).

If you're dealing with a modem/router combo issued by an ISP or a router with SIP ALG forced on, you may have
to use for the Proxy Server. The purpose of is to circumvent
faulty SIP ALG features in routers.

C) a router that allows you to set QoS or assign highest priority to your ATA or IP Phone over all other devices on your LAN (local area network),

For a very general description of what QoS can do for you, visit
The basic idea is if you're torrenting or have a bunch of other computers, smartphones, tablets, etc. downloading and uploading (hogging all your available bandwidth), you don't want
your ATA not to have access to enough bandwidth to make or receive calls properly. So QoS or a Bandwidth Monitor feature (which is just another form of QoS) is a really good idea for VoIP users.

I often get an occasional relative complaining to me, "Hey my calls sound choppy." And then when I go visit, some kids are playing MMOs on a computer, while another person is downloading a huge file,
and another person is backing up files to a cloud service all at the same time someone else is trying to talk on the phone. All those devices, without QoS enabled, are fighting over available bandwidth along with the ATA.

and D) A router that lets you adjust both Unreplied and Assured UDP timeouts.

Thanks to Mango, many of us now understand that in order for ATAs to remain registered and working properly with a VoIP SIP provider like Freephoneline, in particular after power failures, the following conditions must be met:

UDP Unreplied Timeout (in your router) < NAT Keep-alive Interval (in your ATA; for Obihai ATAs this is X_KeepAliveExpires; for Grandstream, the setting is SIP OPTIONS Keep Alive Interval) < UDP Assured Timeout (in your router) < SIP Registration Failure Retry Wait Time (or RegisterRetryInterval in Obihai ATAs)

“<“ means less than.

When a modem leases a new IP address, a problem can arise where prior associations using the old IP address are maintained in the router. When the ATA attempts to communicate using the old IP address, the response is unreplied, and then if the UDP Unreplied timeout is greater than the Keep Alive Interval (and UDP Unreplied timeout is often set to 30 by default in consumer routers) a problem arises where the corrupted connection persists. If UDP Unreplied timeout is, for example, 15, and the NAT Keep Alive Interval is 20, then the corrupted connection will timeout or close. A new connection will be created, and everything will work fine.

Another problem can occur when the Keep-Alive interval is greater than UDP Assured Timeout (often 180 by default in consumer routers): the NAT hole will close due to the ATA not communicating frequently enough with the SIP server. In turn, incoming calls may, intermittently, not reach the ATA. Again, X_KeepAlivesExpires (SIP OPTIONS Keep Alive Interval) is supposed to be 20 with FPL.

Getting access to both UDP Unreplied Timeout and UDP Assured Timeout settings in consumer routers may be difficult, if not impossible. Asuswrt-Merlin (I would avoid any model below/less powerful than an RT-AC68U), third party firmware for Asus routers, does offer easy access to these two settings, which are found under General–>Tools-->Other settings. My understanding is that third party Tomato firmware has these two settings as well. So if your router supports Tomato firmware, that may be another option. Note that I will not be held accountable any damage resulting from failed firmware updates. Apparently, Mikrotik routers also allow users to change both Assured and Unreplied UDP timeout settings as well.

Router firmware that allows users to adjust Assured and Unreplied UDP timeouts include


The keep alive interval for FPL is 20. The SIP Registration Failure Retry Wait Time is 120. I use 15 for UDP Unreplied Timeout and 115 for UDP Assured Timeout.

ISPs do not issue customers routers that can do all four things I just listed. Typically it's far better to have your own router with strong QoS functions and a restricted cone NAT firewall,
disable whatever SIP ALG feature is enabled in the router, and stick whatever modem/router combo your ISP gives you into bridge mode. For Bell Hubs, visit ... r-1993629/. For Rogers, visit ... ridgemodem.

Re: Blocking unwanted calls

PostPosted: 11/03/2022
by fguser100
wonderdollar wrote:Hi,

Is there a way to block unwanted or telemarketers call on Freephoneline.?

Now a days we receive more than 10 - 15 unwanted calls, where no one will talk or leave a voice mail message. Please advise if there is a way to STOP or BLOCK these unwanted calls.



I don't have any solution to provide.

I simply like to mention that in my case, from time to time I get a lot of calls from completely strangers. I answer a few a of them and they all mentionned that I called them previously. Fortunately it last only one day.
I presume that someone use my phone number ( not my line, only my phone number ) to call other people.

Re: Blocking unwanted calls

PostPosted: 11/03/2022
by Liptonbrisk
fguser100 wrote:I presume that someone use my phone number ( not my line, only my phone number ) to call other people.

Yes. It's possible to spoof any outbound phone number.