Everything was fine till yesterday. However, from today I have started facing a very strange problem; seems a sort of call routing problem.
When I make a call to India, the recipient cannot hear me (rather they hear their own voice back). I have tried calling different folks in India many times on five different networks: BSNL, Aircel, Vodafone, Idea and Reliance. The problem occurred with every network except BSNL (Acc to this page: International Long Distance Calls | Verizon Wireless , it should work on all these networks, which it did till yesterday). When I call the same people using my friend's phone (not Verizon), everything works fine.
P.S. I don't face this problem while making local calls, or using Google voice to call those people in India using the same phone.
Solved! Go to Correct Answer
Answering my own question here, in case someone else faces this problem. I called Verizon support and they solved my problem quickly.
Looks like the problem was with HD Voice calling feature, which was not compatible with some service providers in India. I turned off HD calling and voila!! it worked. Thank you Verizon support.