Ok I've heard and had all of these so called problems, let me tell you what's wrong.

The first problem is actually most likely your sim card, and possibly your router, depends, in order to fix this problem I recommend actually contacting t-mobile.

The second problem is the 4.3 os has a memory leak when you use the Alt-esc feature to switch between applications, it slowly looses memory over time to other things, a battery pull is the only way to fix this right now, it's part of the blackberry problem.

Third your using your hotspot browser as your primary browser, go to Options>Advanced Options> Browser And change everything to INTERNET BROWSER, but KEEP THE WAP BROWSER AS T-ZONES.

That should fix most of your problems, feel free to pin me for more details and/or more questions.