Port land line

We have our land line through xfinity. I stopped in to the local xfinity store and said I wanted to take that land line phone number off of xfinity and put it on a trac fone. The service person showed me other options and I declined. I said I wanted my phone number on a trac fone. She said “fine, go buy the trac fone and come back here and I will help you.”When I came back to the xfinity store, we spent another 30 minutes with the trac fone and then she said we can’t do this. Xfinity cannot give your phone number to trac fone.