Apple Watch 5 Series Cellular Activation

I have had nothing but issues and poor customer service since signing up for Xfinity Mobile.  I thought finally I was to the point where I have no need to contact them again for anything, but not the case.  I have been back and forth with multiple reps trying have an Apple Watch added to my account.  I have been to multiple physical stores, spoken with countless telephone reps, and the result is always the same, nothing.  Can anyone help with this?