iPhone having episodes of being unable to send/receive texts and calls after update

Since the last big update, my phone has had 4 instances of not being able to send or receive texts unless from iMessage or make or receive calls to/from anyone. I only find out that it is happening when I try to send a text and it just won't send or when I can't make phone calls. The only thing that fixes it is turning the phone off for several minutes (just off and back on does not work) before turning it back on.