Someone else’s Netflix account on my virgin box and I’m being charged!!!!

Since November 2023 I have seen a £17.99 netflix charge on my virgin bill. I called in November as I paid separately for Netflix direct with them and not through virgin. A credit was applied and I was told the only way to stop this was to cancel my Netflix account and restart it!! I cancelled my account and haven’t restarted it but each month there is a charge on my bill for £17.99  for Netflix which I have not activated on my account. I call and get told a credit will be applied and this will be looked into and won’t happen again. Yet again I have just checked and Netflix has been activated on my account (not by me!!) and I will be charged again this month. I have just been on the Netflix Channel on my virgin tv box (204) and there is actually someone else’s Netflix account signed in!!! I do not recognise the names and am unable to sign out as the account is pin protected!!! So can’t see the email address linked to it either. How do I sort this and remove this account and stop the monthly charges and having to call each month!!! Really not happy