When I got the phone and had the SIM card installed by AT&t it too would only work on WIFI. I did some digging and found that the SIM card has an assembly surrounding it which holds the SIM card in place. I had purchased the insurance for this product. The phone was never shipped with this SIM card holder. I asked to have the sim card holder shipped to me, 2 months and still waiting. Garbage customer service. I had to purchase it from AT&T. Now the phone works perfectly. Great phone garbage retailer, insurance is worthless.