problem activating Galaxy 5 watch with Note 20 Ultra

I purchased the Galaxy watch 5 LTE model @ a Samsung store with the hopes of activating it with phone so they it can be used independently (for ex. If I went to gym with the watch I could leave my phone at home).

I have spoken to at least 5 reps at t mobile and once I give them the IMEI they say the watch is incompatible and cannot get its own line. 

When I try to get a line through the wear app it tells me to call sprint/ tmobile.

I called Samsung and they ensured me it should work just fine once tmobile links my watch to my phone services to share data, calls and texts.

Tmobile says if i purchase the watch directly through them it will work but I do not want to do that and it honestly doesnt make sense that I would have to.

I'm unsure as to who is right and if this is possible. Ayuda.