Why won't T-Mobile deliver on what they promise?

I live in the Dothan, Alabama area. Actually in Houston County. I have had T-Mobile home internet for about a year. For the most part it has been okay. Especially during the day. But come evening, it goes down to 1Mbps or less. I have called several times to complain and I am given the same ole song and dance from customer service. “they must be working on the towers”. Really? So what your telling me is that the maintenance crews only work at night in my area?

 Lately, I have been getting 100+ Mbps. I thought great! They finally got this thing working. But just two days ago it went from 100 Mbps down to 6 Mbps during the day to less than 1 Mbps in the evening.  

 I saw an Xfinity truck parked in front of my house yesterday. Out of curiosity, I went and talked to the driver. He explained that Xfinity is going to be running broadband down my street in a couple of months and he was just checking the area out.  

So maybe I will have to go with them. It might cost more, but at least it will be a constant speed!