Default Still having bad connection with new modem

How do I check if my T-Mobile phone is roaming correctly on AT&Ts voice network? I can find the data roaming option under settings but since I have updated to 4.3 ROMs and above the voice roaming setting disappeared.

I have T-Mobile postpaid non-contract so I should be able to voice roam on AT&T for free. I am having spotty coverage issues after updating to 4.3 ROM and I have verified that I am on new MK2 modem that I successfully loaded through ODIN. The last time I had this spotty issue it was caused by a ROM that turned off my voice roaming. Does anyone know easy way to check whether voice roaming is enabled? There is a big difference between T-Mobile's prepaid and postpaid networks in Southern California.

I am running Infamous 9 with ktoon kernel.