Could be something with 4g. My 3g flip phone is working fine (AT&T subscription plan - not prepaid). I can even receive calls from people on T-mobile who are

Could be something with 4g. My 3g flip phone is working fine (AT&T subscription plan - not prepaid). I can even receive calls from people on T-mobile who aren't able to call each other or other people (although they don't receive my incoming calls). Another bonus for avoiding the spy phone.