Sometimes contact shows up as name other times as phone number
so i just got an iphone 4s for verizon and the guy at apple transfered my contacts for me in the store. Sometimes when i get texts or even phone calls like from my mom for example it will just show up as her phone number even though i have her in my phone as "mom" sometimes there will be a 1-xxx-xxx-xxxx in front of the area code and other times there wont be. I have to add both versions of the phone number 1-xxx... and just regular xxx-xxx-xxxx. this doesnt seem right. Is there anything i should do to fix my contact problem??
iPhone 4S, iOS 5.0.1, Verizon network