You appear to have two separate issues, but with potentially one commonality
1: Mobile network coverage - are your 2 phones having problems with coverage just at home? Or in other locations as well?
2: WiFi coverage - I presume you're referring to WiFi-calling when you mention about problems calling. Same question here, do other internet-based functions work OK? Do you have similar problems when using other wireless routers?
Do you still have your old phones to test with? WiFi is a connection between a mobile device (phone/tablet/laptop) and wireless router, it's separate from a mobile-network connection. But in your specific case, it's interesting that problems with both, have started since having new devices - suspicion must lie there to begin with.
