Switch from T-Mobile to AT&T 1 1/2 weeks ago and got the S4. I have troubles receiving texts from others(iphone and non iphone users). Incoming texts would be received 30 minutes later or sometimes none at all... calls are the same, when others tried calling me it will ring 2x then go straight to (this user has not yet establish a voice mailbox system blah blah blah etc...) I always have signal when i notice these problems and these problems happen way too often. Anybody else have problem with this?