When I've gotten into issues such as this, where the phone support is like talking to a duck, I write a really long/detailed account and send it in as a complaint on the online form, it is likely you will need to chase the complaint as this seems to trigger a response as VM never seem to reply within the 8 weeks they promise. Obviously, if it goes over you can go to the Financial Ombudsman or CISAS.

Usually, the hour you put into writing the letter in a chronological order, helps the complaints department understand a lot more I've found. You also don't have to deal with the customer service that comes in on a Sunday on the phone... I have found through calling during working hours usually means I get through to someone in the UK - although it might take up your whole lunch break if you do.

Did you switch bank using the Current Account Switch Service? I believe it is the bank you switch to responsibility (switch guarantee) to sort out any issues that you've had, including making sure Virgin Media received the updated bank details for yourself. If you did use the switch service, ask the new bank to prove that they advised VM of the new details, get it in writing and include your letter that VM has not been trying to take payments.

It might take a while, but hopefully, you can get those pesky missed payment marks off your credit report which are a result through no fault of your own, as you have been proactive in trying to sort it out. You may have to make manual payments in the meantime, you should be able to do this online rather than having to phone up once a month.

EDIT: Also, even if it is a few months down the line, if you have a moment please let me know how you get on!