IMEI/Compatibility for Xfinity Mobile

I recently  signed up for the xfinity mobile offer with my new internet plan, and you guessed it, the IMEI check says my phone is not compatible. But I know it is compatible because I currently use it with Infimobile prepaid (which is also a Verizon MVNO, just like Xfinity is) and everything is working fine (voice, voLTE, SMS, data, everything is working). So I'm looking for someone please to provide a  direct message link to support, so that I can provide them the IMEI and whatever else they need to get a "compatibility whitelist" for my phone (so that I can get a SIM).

Background: The phone is carrier unlocked (long since paid off), works with Verizon (as I already said),  everything is in order. The local Xfinity store does not possess the skill or knowledge needed to fix my problem on site. They get stuck at the "we can't get you a SIM because your phone IMEI does not pass the compatibility check".

Thx.