I stopped by T-Mobile today. I explained that I wanted a prepaid phone but planned to use their sim in a tracker. The knowledgeable salesman said "no way that would work. Our sims only work in phones. " I left there and I got online and did an online chat with AT&T. I was informed that I could activate their sim online without purchasing or using a phone. So, I purchased an AT&T sim for $5.00. I will update whenever it all gets here and I try to start setting it up. The tracker was shipped from China today, so it might be quite a while.......