No you shouldnt have to pay a fee or anything, a month ago i just switched sims from my LG Flex to my old iphone 4 bc i caouldnt stand android anymore, got my iphone 4 stolen two weeks ago, and just went to go get a new sim to use back on my LG Flex, this past Saturday, i received an iPhone 5 i bought off eBay went straight to the AT&T store and asked to activate a nano SIM for my 5, no charge at all. They always tell me they "waived" the $10 for the price of the SIM card but its all bs, they gives those puppies out like candy (other occasion i swtiched to Tmobile and gave my brother my older iphone 5 that i would activate over the phone, AT&T store employee said here you go, no questions asked.)