Poor Cell Reception in my house. Do I need a Cell Signal Booster? Any recommendations?

In many areas … T-Mobile is not ‘interested’ in fixing service, especially rural areas.

There are large areas that T-Mobile claims to have service … but does not.  I have been down this road for ~9 years in parts of California.  Some areas - they will set up roaming … other areas, they’ll tell you to port.  I have escalated many areas to BBB/CPUC and FCC.  Unless there is pressure to deploy or .. cheap / easy land - they typically won’t deploy in many rural areas.  I’m assuming you’re in a rural area (or at least suburban/exurban) BTW.