Why is my phone/sim card doing this? T-mobile?

[Izzy]

I've had my T-mobile phone for just a little over a year. I've only had this problem happen one other time. My boyfriend on the other hand, has had the same problem I'm having now, several times. The problems are, not sending text messages, repeatedly getting the same message from someone over and over again, wont make phone calls, sometimes it start calling someone or emergency numbers by its self, and it wont delete text messages either. It will just sit there for hour's saying "deleting". I had this happen to me a few months ago and all T-mobile did was say my phone was the problem and they gave me a new one. Well I'm finding it very hard to believe it was my phone, especially since my boyfriend had the same problem. But I switched from my Gravity T to the Gravity 3 and it's still having the same problems. I honestly don't know what to do. Should I just go to T-mobile again or is there something I can do? My mom isn't really wanting to have to spend more money on my phone, she's already spend 50+ just to buy the phone and have it fixed.