I had this problem as well when I was first trying to setup my phone. I would insert my SIM Card and it would say NO SIM. Talk about getting frustrated!! THEN I was trying to troubleshoot the problem myself and realized that my SIM Card was a NANO SIM (which just means that it is smaller than the typical SIM Card) so I contacted my carrier and they have this small little carrier for the Nano SIM Cards and once I inserted it back into my phone IT WORKED!!!! I was ever so happy because I thought I was SOL with my new phone.