Paying off your tab does not impact your network quality. Are others in your home/area experiencing the same issue? Have you restarted your phone?  

You can use this map to find the cell towers nearest to you https://www.ertyu.org/steven_nikkel/cancellsites.html

When I experienced a drop in network quality I found out a tower was taken down due to the library undergoing major renovations. 

I see, a tower is quite far from me. Thank you