home internet is terrible now

We’ve had the T-Mobile home internet for almost 2 years now. It was ok no great speeds but live able. About 7 months ago it really slowed way down. I picked up another gateway and went to an external(Waveform) antenna. It made it better at times but still would almost be nonexistent at times throughout the day. Out of curiosity I plugged my address into T-Mobile home internet availability and it says not available in your area!!!  Has this happened to anyone else?