Iphone 7 AT&T Cellular network not working

Iphne 7 users with AT&T carrier services, how well does your phone connects to cellular network? My iphone is hardly ever well connected to cellular network. Everytime I tried to use cellular network, it takes about 30 seconds to propery connect to cellular network. I also have iphone 6s with Verizon for work but iphone 6s connects to cellular network much faster and better almost everyday! I have been using my phone for a year and a half and I have been patient enough to stand with it but from time to time and now I just can’t stand it! My galaxy 2s that I used 7 years ago connected to cellular network much better! This is ridiculous!