I have the nexus 4 on At&t, replaced my old Iphone 4s. I still have 1 year to go on contract. I'm on the 200mb plan and I work out of town twice for 2 days. hotel I use has no wifi, I bought a T-mobile prepaid sim card. I just want to use the T mobile $3 or $2 daily deal for unlimited internet. does switch cards back and forth cause any problems with the phone. I know I just won't get any calls. thanks