If you are not sure they are active Public Mobile customers any longer and you cannot confirm this, then there is not much you can do. But if you know they are still active Public Mobile customers and you can (or they can) confirm this, then definitely bring it to the moderators.
Hopefully, this is just a glitch in the system and it will correct itself on your account. There has been posts about phantom extra $1's on account but no phone number listed to match. These these right-side themselves, sometimes it appears.
IF you know who's who and what's what compare it on your SELF SERVE account by clicking on the arrow pointing to the right, which will open up the list and the arrow will then point down.