Free Mobile Line - but hate the phone

I have a bundle... high speed internet & free mobile line.  The catch on this is that I have to use the Motorola phone sent my Xfinity in order to get the bundled deal.
I said yes to that and have been using the phone for 5 months.  I absolutely HATE it.  I really want to be able to use the phone I was using before switching to Xfinity mobile!!!
If I keep the phone they sent (I think it's like $5 per month), can I take the SIM card out and use it in my Pixel phone instead?  Without losing my bundle price?