For the last few weeks, I have had issues with data service. There is a strong signal, but I can't send or receive iMessages and I can't open or load apps. Sometimes I can restart the phone or turn off the cellular date and back on, then it works. But then it will just stop working again after awhile.
I have an iPhone 4s and have had great service up till now (I've been using Straight Talk since May of 2015), so I don't understand why all these problems have come up all of a sudden.
Any ideas?