House move VM account transfer gone wrong?

I write on behalf of my elderly mother-in-law (who is the VM customer, with a contract running until October 2024), who recently moved home. We logged the move with VM, got the installation at the new property booked, and all was installed as planned by a friendly and thorough technician.

So far, so good.

I manage her account online and, superficially, things there appeared normal. However, she has now received a letter stating that payment of her bill has not gone through. Digging around online (she's misplaced the letter, which I'm sure will turn up, so I can't verify the actual wording), I can see that her account now states she's left VM.

Something's obviously not gone right somewhere.

I suspect the issue may stem from the fact that she lost her husband – the original account holder – in 2022 and it took an unimaginable amount of effort to transfer the account over to her (to their credit, VM Community staff eventually came to the rescue and sorted things)... but she was also in the VM system as a Virgin Mobile user and perhaps something, somewhere hasn't been updated correctly.

She is however understandably stressed by the situation so we would very much appreciate some assistance in trying to work out what has gone wrong, how we can fix it, and of course get her bill(s) paid!

Thank you