Help transferring a number

(sorry question uploaded on wrong phone, re-uploaded)

When we updated, we had an issue with the website and billing/credit card. Retention (?) worked it as a bill to my account and waived the connection fee since it is a technical issue.

We are wanting to transfer our mom's current phone to our account, but I know we will run into the same issue with billing (I have tried more than a few times).

Since I would prefer to do it online, but can't, how can I get a hold of someone who can understand the situation easily?