5G never works!!!

I just recently made the mistake of switching from Verizon to T-Mobile. I've never had connection problems with Verizon. The minute I switched to T-Mobile I was no longer able to use the internet on my phone without being connected to Wi-Fi. It doesn't matter where I am, the 5G never works. I have downloaded internet speed tests to check the 5G and regardless of where I am, I receive a poor connection. The speed test shows I'm currently using a tower 20 miles from my location. When I contacted T-Mobile, they said nothing was wrong with my service and offered to send me a new phone. I'm waiting to receive the new one but I am not expecting much to change based on all the horrible reviews I've been reading.