5g reception

We just got the new iPhone 13 Pro Max (2phones) and the 5g and signal reception at our house is totally crap. No one can hear us properly and we lose calls all day long. What is the problem? We've adjusted settings. Turned off 5g. Rebooted. Help! I've tried everything from the online advise and forums. It seems like the 5g signal is the issue as we had great reception previously.