I have an Iphone 4 and am having some issues with some Samsung friends - I'm with Koodo, the 3 I know of are with Bell... I can receive texts from my kids' father but he doesn't get my response, and 2 friends receive my messages but I don't receive their replies. I've tried removing the sim card, resetting network to default settings, deleting the previous messages and contact info and trying to just manually input the phone number - nothing has worked. And this just STOPPED working - had had no trouble up until last week, and as late as last night with one of my friends - help!!!!