why TMobile home internet so bad

We had great service from T mobile for 5 months.  20 to 30 M speeds.  Now we are lucky to get 2. Can't stream TV or play games.  I lost the connection to my Tmobile phone as well.  They have done something with their network or our account. Did they shutdown the Sprint towers?  I have been on with Tech support for hours, gone to the store and no help. They sent me a new tower.  No difference.  I asked about a new sim card and they said that was not the issue.  Tmobile kind of just threw up their hands and said go somewhere else.  The problem is we don't have any other options.  Sucks!!!!!