Problems after system update

Thank you for your reply!

1. I have had three conversations (on different days) about my problem with T-Mobile Technical Support, which did not result in getting the problem fixed.
2. During this process, I have restarted my phone multiple times.
3. I'm not sure if a network reset has been done (it might have been done by T-Mobile Technical Support). Is this something that I can do, or is it something that would need to be done by T-Mobile?
4. The problem exists for all incoming calls.
5. Outgoing calls can be made (if I make multiple attempts), text messaging works, and I can access the Internet. (My voice mail was working until T-Mobile Technical Support turned it off to see if calls would come through--they didn't. Now it doesn't work, even though T-Mobile says it has been reactivated.)
6. Since the problem was caused by the installation of a system update on July 31 (the same thing happened on my wife’s phone), do you know if there is a way to uninstall that update?

¡Gracias de antemano!