My iPhone shows I have wifi but no LTE bars

On my phone it shows I have wifi but no LTE bars, I have tried restarting my phone, turning wifi off then back on, and turning airplane mode on waiting 5 seconds then turning it back off, and nothing happened. The main issues are, that I can't receive phone calls but I can make them, having really slow wifi even when I'm by the router, and I'm the only one that's connected to the wifi it's happening to. Any suggestions on what I should do?

[Re-Titled by Moderator]