Att micro cell

I have noticed when The iPhone 4s will not connect to The AT&T 3G microcell. However the iPhone 5C seems to work just fine. What is the deal is it a new update is it apples iOS 7.1.0.4. Have a microcell for about three weeks now in the iPhone 4s is not doing good but the 5C is. Is this a 3G 4G or LTE incompatibility issue???? I hope this will be fixed soon because everything I do such as turn off or on airplane mode disconnect reconnect to Wi-Fi nothing will work. I have also for similar issues with the android phones. Please leave your comments to this post I would like to hear your feedback on how to fix this problem. I will also try to do some more research on how to fix this. Microcell is not white but you lack it is one of the newer ones salesman from AT&T did not even recognize it.