Doesn't hurt to check the APN settings. The only reason I'm suggesting it is because that's what happened to my son's phone it was working fine and it suddenly stopped working so when we checked the APN settings they were switched to Koodo APN settings and PM was missing.
Since the OP mentioned iPhone 7S, APN settings aren't really a factor (APN cannot be set on iPhones on most/all North American carriers since these are configured through the Carrier Profile); it's more likely to be something like a network profile. See this thread for more info.
We solved it... Thanks for the tips though... all part of the learning process.
Yep, saw that... glad it's working for you now! I just posted the follow-up so that anyone else reading these threads/posts in the future have some direction.