No Cellular Service On Phone

My iPhone 6 has been having some issues with it's cellular service. The phone will say no service, and so I turn the phone into airplane mode to restart the signal. The phone will continue to search for service, but won't pick any service and just continue searching.

Before I would restart all setting and this would fix the phone for a few days. Now I tried to do this and my phone won't pick up anything. I can pick up wi-fi and bluetooth fine with zero issues. I reset all my settings and content as if it was a brand new phone and it still doesn't work.

Is there any way to fix this? Also if I need a part to change out what would I need?