I cant speak to anyone as I have trouble understanding them due to their accents and find they just read off a script and don't really listen to what you say.
Im sure that when the Direct Debit is cancelled they will find a way to contact me
I can assure you they won't. Your account will simply be processed as late payment, then defaulted, VM will add late payment charges and then pass the debt to scumbag debt collectors (and they will contact you), and VM will also notify credit reference agencies that you are a defaulter, which will mess up your credit history for the next six years. That'll be visible to service suppliers, lenders, landlords or mortgage providers, even employers.
I agree VM's attempts to make cancelling difficult are unfair (and they're a breach of regulations), but rather than trying to engage with the imbeciles VM have on the end of the telephone, give your 30 days notice of cancellation by post, using recorded delivery. Address at section M of the terms and conditions. Don't expect any confirmation, VM aren't that civilised. As a 14 day cooling off period reverts to any previous status of contract, exercising your cooling off rights should also put you back into your notice period, make sure the letter is clear on that, and that the previous cancellation and contract end date are to be reinstated. VM aren't very good at basic account admin so keep it simple and precise.