slow speed

Hi. In my situation, the phone dropped dramatically in the past year, and especially in the past 5-6 months.I used to get 20 to 100 pretty consistently last year. 

Yesterday i ran some tests while driving from church back home. At one point, my phone got 358.9 down and 74.2 up!! Of course, I could see the tower right in front of me. The speed continued to drop as I got closer to home, which was about 1.5 miles away. By the time i got to my driveway, I was back down to 2.3 up and .5 down. I tried the home internet but took it back as the unlimited plan is not available at my address, only the lite plan. The speed was slightly than my phone, even when in the same room, but still not very fast. I submitted a ticket to Tmobile but they said speed would vary because of congestion. If that is the case, they need to increase capacity. Been with tem close to ten years and would like this to be fixed.