Mystery Debits

Every month from Oct 2022 I've been debited £7.00 by Virgin Media. This is never reflected in my monthly billing statements from VM. I contacted VM and explained the situation through messaging and was told to contact O2. I have 3 numbers with O2, two are legacy numbers which were switched over from Virgin Mobile. This £7.00 never appears in my billing from O2. I discussed the matter with O2 and they had no idea what this charge was for. They forwarded me back to VM where another discussion failed to indicate the purpose of the payment. I was forwarded on to Virgin Mobile where I received a message that their offices were closed. This seemed strange at 3:30 on a Monday.

The only thing I can think of is that it might be a legacy of the last time I updated my phone with VM, but that was some time ago now. At any rate, I'm just hoping that someone can direct me to where I can find out. 

Thanks

Stephen