Onstar Plan not transferring on used vehicle purchase

I purchased a used 2025 Hummer EV SUV.

I was told that the remaining time of OnStar One would transfer from the original owner.  A couple of representatives have confirmed this, and every time I call, they say they are working on it and extend a trial for 30 more days.

I was told numerous times that a representative would call me back.  They never do.  

I asked for a supervisor, and never get one.  

I am currently on hold with a representative named Jalia.  They have no respect for how much time this is taking.  What is going on with the customer service there, and why can't anyone there seem to figure this out?