Mine has started to have not as great of reception but I also painted my case and chalked it up to that.
How long has it been going on? Did you try a battery pull? If not try that and if that fails call AT&T and get it switched (if still under warranty)
first thing I did was a battery pull. I missed a call while the phone was in my pocket searching for network. I also have a Moto Q and it holds reception very well. I really want to keep the Curve. If this happens more often I may be forced to go back to my Q. Call reception and quality is at the top of my list.