After having my Note 5 for only a few days I realized something strange. Whenever I was on a call using my BT headset I could not turn mobile data on. Once the call was over and I hung up, then I could turn the mobile data on. I tried various fixes, including resetting the phone, but nothing changed. I spoke with T-Mobile at length about this issue and they could not figure it out, either. When I had the Galaxy S3 with Boost, I never had this problem.
This was very disappointing, because I really liked the Note 5. Also, after some inquiries to find a T-Mobile store close to me, I discovered that there used to be 2 T-Mobile stores in the town just north of me, but they had closed down because their coverage was so bad in that town. More research proved that T-Mobile's coverage wasn't the greatest in my area.
Thankfully I am on T-Mobile's test drive so I am returning the phone and going back to Boost.