T-mobile Note 2 on At&t having issues.

[lunchmeay78]

I looked everywhere and cannot even come up a guess to my issue. I have an unlocked T-Mobile Galaxy Note 2, but switched carriers to AT&T and now having weird issues with the phone. I changed the APN settings, but I still get network drops during phone calls and syncing issues with phone numbers.

The phone will randomly drop a call and not be able to call back for about 5 minutes. I am not a noob and I can usually troubleshoot my own issues. Oh yeah, the phone was working fine on T-Mobile and only started the issues when I put a fresh AT&T sim card in it. It doesn't happen all the time either. I could go a week no problem, then three or four days with issues.

Any suggestions on what I should do?

Thanks a ton