Wondering is this is caused by the fact that the iPhone 4 (still IOS6) is a CDMA only device. When talking on the phone and a text message is received the call is dropped. I know that with CDMA only one thing at a time can be done, cannot browse web and be on a call at the same time for example. Am wondering if the call drop is another example of the limitation of CDMA. Cannot upgrade phone until next June unfortunately without paying "full" price. This is the wife's phone and she gets lots of text messages and is on calls a lot.