AT&T has been working on their 5G network and continue to. There are apps that can also monitor your cellular connection. Just because you see bars doesnt mean you are connected or at what speed. try "opensignal" in the app store! Notes have also been known for slow wifi and AT&T wifi monitor can cause issues. Try disabling it and try reseting your networks.
Call Asurion through the AT&T Pro Tech app. Tell them you are having connection issues. Ask them to check for reported issues in your area. Then ask them to do a complete reset your network connection. Should be settings, then connections, then more connections, at the bottom is the reset. This will reset ALL your connections G5/LTE/WIFI and Bluetooth. But NOT your phone.