We have five lines with Sprint. For the last 6 months we have been dropping calls only on the iPhone 4S. Last night on my iPhone 4 I had no problems with connection over a 90 minute phone call to China. But, my wife on her iPhone 4S can't make a five minute phone call without losing the call 3 times. My son and daughters all have Android phones and never drop a call. I have had 5 conversations / chats with Sprint. We have reset the phone, we have checked on towers, etc. The phone just seems to not like the new Sprint network.