I have Shaw Cable, an Arris/Motorola SBG6782-AC cable modem/router, and have hooked up a Yealink W52P Dect SIP phone + three associated handsets after paying for the Freephoneline unlock code.
The phones work, can make and receive calls and voice quality is good. Except:
1) calling a direct line at an organization (in this case a university) gets redirected to that organization's switchboard. i.e. calling a person with a direct number (no extension) and it gets redirected to a voice recording that says "This is the main line, please type in the extension of the employee you wish to talk to". Very strange since it was a direct phone number. The direct number works when calling from another source (like my cell phone).
2) Toll free numbers seem ok, except for one 866 number I tried. It always results in call failure from the SIP phone. But can call it with the cell no problem.
3) Calling my own cell phone is really strange. It gets through without issue maybe 1 in 10 times. For the other 9 tries, the Yealink shows call failure and appears to disconnect BUT my cell phone rings and connects to dead space if it's answered! The cell will show the phone connection live and counting, while the Yealink handset is definitely showing that it is disconnected. BUT, if I then call in again from the Yealink while the cell is still thinking it's on a line, the Yealink gets through! The cell registers another call and I have the option of accepting it and terminating the old call. In this way, it establishes a good connection with the Yealink. It's like I have to make a path the first time, and the followup call seems to always work if the cell has the first call open to the dead air that was created.
Very strange unique issues with specific phone numbers. It's hard to troubleshoot, vs. a global problem like "all call's out fail, or incoming calls go directly to voice mail" or something like that.
Any ideas?

jbo