Can't make voice calls anymore from cellphone at Home

Our HTC One phones worked great on VM for about a month when suddenly they couldn't make or receive calls or SMS messages. If we leave our area drive a couple miles away, we can
use the phones fully. As it is, for the passed 3 days, when we are at or near or home, we only have 3G connectivity but not Voice/SMS. Numerous calls to VM have proven fruitless as they don't seem to have any real tech support, only folks with heavy foreign accents following the same script that doesn't help.

We have verified that our VM account is still active and like I said the phones work anywhere but in our neighborhood, even though we have max bars for signal strength.
In our neighborhood, we only have the data connectivity, not voice or SMS. Have also tried re-activating the phones without success (even though the activation process says
the phone was activated successfully). Have verified my

Can anyone resolve this mystery? At wits end.

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See the second part of my blog here:
HTC EVO 4G: resolve connectivity issues - Blogs - Cell Phone Forums