IPhone 5s no connection/service?

My iPhone 5s usually says "LTE" next to the AT&T logo in the top left corner of the phone, but today the "LTE" icon wasn't there, I can't send texts or use the internet or use snapchat, twitter, instagram, any of that without using Wi-Fi. Everything was working just fine this morning, I checked my phone a few hours later, opened up Safari to search something and it wouldn't load, same thing with messages and apps, failing to send, etc. What is wrong and what do I need to do? Also, sorry for sounding oblivious I'm not really too knowledgable with these kinds of things.

Is it showing 1x? And if so, it could be the area or if you go to an area where you know you have good cellular service, try restarting your phone. That may be the trick. I took a computer class and my teacher has told us and always emphasized on this… "When in doubt, restart." I use that with a lot of stuff and it always seems to fix a lot of stuff. May seem complicated but sometimes you don't have to overthink it. Hope this helps.

Settings - general - reset - reset network settings