Hello sir. my voice call is not working, You may hear drop outs or poor sound quality in this call. Your Internet connection currently has reliability problems, perhaps due to a weak WiFi signal. every time this message show after call

It is because your internet connection is not good stable or not good enough for making voice calls...
To check this, Click on Start >> RUN... Type CMD and click on OK.
In Command Prompt, type ping 4.2.2.2 (space after ping) and press enter
it will give you result like this:
C:\Users\abhishek.tripathi>ping 4.2.2.2
Pinging 4.2.2.2 with 32 bytes of data: Reply from 4.2.2.2: bytes=32 time=309ms TTL=57 Reply from 4.2.2.2: bytes=32 time=275ms TTL=57 Reply from 4.2.2.2: bytes=32 time=276ms TTL=57 Reply from 4.2.2.2: bytes=32 time=275ms TTL=57
Ping statistics for 4.2.2.2: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 275ms, Maximum = 309ms, Average = 283ms
If you get 4r replies, than your internet connection is fine. Is any of the line says "Request Time Out" then it is clearly a problem with your Internet Connection.