if your phone is glitchy, running slow, or you're having issues sending/receiving text, imessage, and phone calls. Try these simple steps before you make that call to tech support, 9 times out of 10 it will resolve the issue.
Restart your phone (power cycle). Toggle into and then back out of airplane mode. Manually select a network (you can do this under your devices "network settings"). Remove and reinsert your SIM card. (you can even try testing it in another device, preferably a network specific device).
make sure a recent app install isn't causing the issue, if so remove it and restart your device.
finally, if you've locked yourself out reset it...nuclear warfare. and next time don't forget you access. Hope this helps.