I have an iphone running iOS 6.1.6 and I do not subscribe to a Telus data plan. It seems that I cannot receive texts from my friend (who also has an iphone) unless I have wifi internet connectivity. She is not on the Telus network. I can send messages to her without internet, but not receive hers. She is running iOS 7.1.1. I do not have the same problem receiving texts from Android devices. What can I do?