Ordering a new SIM card

I have an old SIM card. It was actually part of the pilot program and lately my cellular data stopped working. WiFi works, BT and everything else works. I logged into my account online and selected my device. There was an option to replace the device via BYOD right online. So I went through the compatability checks just fine but when I selected to keep my number it failed. It would only work if I selected a new number. I've had this number since Xfinity Mobile started. I can't just replace it with a new number.  I do not know what to do from here. The only thing I can think of is Xfinity Mobile does not allow customers to keep the same number on an active line that already is there. Xfinity please help!