Not true. The SIM controls the 3g cpmodem AND the seperate LTEmodem. With everyone that I have talked to about this(12) 12 out of 12 had the problem fixed by simply replacing the SIM card. Had the radio(cpmodem) crapped out, a SIM replacement would not have fixed this issue.kvswim said:It's not the SIM. You would have issues with 4G if it was. Sounds like your 3G radio crapped out on you. It's happened to a few of us....the 3G/4G switching seems to be hard on the 3G radio. Not a huge deal if you're in warranty and/or live in a 4G area.