There's a pattern emerging that VM have made the cancellation process as poor and discouraging as they possibly can, but there's a few things you can do.
You may want to cancel by post. If cancelling by letter, allow for the delivery time, ideally specify a date that the services are to end given the 30 days notice you have to give, and use a recorded delivery service. If you want to stand on your rights, don't allow for the postal delays, and make the start of the 30 days when you tried to cancel by phone and VM made that impossible, but if doing this don't be surprised if it is in some way incompetently processed. Most postal cancellations get sorted out, there's some that are bungled, so you want to have evidence in case things go wrong.
In terms of the fact that they didn't action a cancellation request, they owe you anything they've charged since the original date (allowing for 30 days notice), and they owe you compensation for the appalling customer service. If forum staff leap into action to sort out both you need do nothing, but if they fall short on either correcting the situation, or compensation (I'd suggest around £150) raise a written complaint to Virgin Media about the poor customer service, and demand compensation for that, and the resultant delays in being able to cancel. This will be fobbed off because VM handle complaints with the conspicuous skill and quality of all their other customer contact activity, but if you're still feeling the need, you can then escalate to the industry complaints scheme CISAS and ask them to get compensation out of VM. That will be slow because you need to have allowed eight weeks from the date VM received that complaint before you can involve CISAS, or you don't need to wait eight weeks if you reject any VM "resolution" and demand and receive a deadlock letter. Doesn't matter if VM close, lose or ignore your complaint - so long as you have a complaint reference number you can still use CISAS.
I've seen repeated reports of difficulty when trying to cancel by phone, with customers being passed round multiple unhelpful staff, left on hold, disconnected, bounced from phone to Whatsapp and back again. This is a flagrant breach of Ofcom's rules, specifically General Condition C1.8 specifically paragraphs 1.13, 1.14 and 1.15, so I'd strongly recommend you complain to Ofcom. They won't intervene in your complaint directly, but Virgin Media are setting themselves up for a big fat fine over their repeated breaches of this rule.
