It's CINGULAR. It sucks. I switched to Sprint using the same Razr. I haven't had a dropped call since. Sprint isn't perfect, but it has some advantages with internet speed, using CDMA. I would go with Verizon if you wanted a GSM phone.
Pretty sure Verizon isn't GSM It is CDMA as well... or so it used to be.
That said if the phone doesn't come in two models CDMA and GSM then there will be no purchase buy me... sprint is the one I have and won't be switching thouh they aren't that great.
I stay with sprint because its the only place that offers unlimited text. Well as of 3 years ago. Now I think tMobile does for 10-15 a month so they are caught up, but cingular and verizon still have a while...