Update as of 5th August, 7 AM
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1. Vonage is still having the same problem
2. Skype is working fine
3. Thank you ishtah. That's the right thing to do. That's what exactly I did 3 days back.
Call Q-Tel. Ask for somebody from Technical Services. Slowly tell them that all on a sudden you are having problem with VOIP specially Vonage.
Also mention them, high latnecy causes this problem, as Vonage works when the latency is less than 120 ms.

When more people speak to QTel, there is a better chance they might try to solve the issue.

4.To NDIAPhil & whiskeydelta-->
IP address to tracert : 69.59.224.28

Steps for Windows XP & Vista :
a)XP: Go to Start --> Run --> Type cmd and hit enter
Vista: Go to Start --> Type cmd and hit enter

b) type tracert 69.59.224.28 and enter

When tracert is finished, you will notice consistent higher latency (if anything more than 120ms)
That is why our vonage is not working, we get distorted voice.

If anybody has any other update, please feel free to post here.

Cheers