I had a similar thing for my mother with Vodafone a couple of years ago.
I was involved in 2015 emailing and writing letters on her behalf which took a year to July 2016 for it to be finished with and for her to receive compensation in her bank. It had begun in 2014 or earlier
There was no theft, just closing an account shortly before the final date, she gave them notice and it should have closed as at the expiry date, but they didn’t stop it.
She checks her accounts so found out another payment had been taken and called them back. This second time they successfully stopped the account, but never got the admin right for the original notice and the Vodafone system kept her listed in debt for an extra month
It would go away for a while then a debt collection company would contact her, they didn’t buy the debt so were acting on Vodafone’s behalf. We managed to get the debt collection company to keep rejecting the debt and refer back to vodafone
Vodafone would end it and annotate the account but never remove the debt balance, so it would trigger a month or two later and start all over again
We had giant chains of letters and emails with a debt company, the ombudsman, customer services, accounts, the Vodafone CEO and their PA. As noted above it took over 2 years for them to clear it off the account
As the have spoken to call centres and never had the account stopped, didn’t monitor what was being paid and only ended up by not paying there is a ‘valid’ debt in place and it now looks like they are making excuses to not pay a debt they have ignored