Cannot call non-FPL number

[kenjliang]

I am inside an Intranet and using ATA. I am able to call FPL number and talk normally. However it has following issues:

1. when calling non-FPL number, I hear nothing on my side, the FPL log shows the call was successfully connected.
2. when non-FPL number calling me, my phone rings, but both sides hear nothing after I answered.
3. when talking with FPL number, the call will be cut off after some time, it varys from few minutes to couple hours.
4. the soft phone cannot connect to server.

I know for sure it is the Intranet setting issue because the same ATA works fine when I connect it directly to Internet. Since I have no right to investigate the Intranet setting dirrectly, can anyone suggest what could be the cause then I may ask admin to check? Please be as precise as possible.

Thanks for any help.