I understand. But, have you tried putting the sim card in the phone (Pixel 3XL)? Won't hurt to try...plus I don't know how often the IMEI information is updated on Visible's end? I had a Pixel 3a on Visible and it worked without issue.
I just found out from a reliable source that Visible started supporting the Pixel 3 and 3XL on June 21st, 2019.
I also have this issue. Yet I have been a Visible customer, with my Pixel 3Xl for 1+ years now. I chatted with a rep about the new Visible and Visible+ plan changes, and was told that my IMEI says that my phone is not compatible with Visible (at all). Yet is does work. And the Verizon network says it is compatible. I wonder if they have a database error. My Visible rep could not tell me if or when my phone would stop working on their system. Very frustrating!