Your past topics don't provide too much detail of the issue but cancelling your direct debit is only likely to compound your problems with VM.
Whatever the rights or wrongs of your case, if VM is expecting a direct debit payment, which then fails, it sets in motion VM's debt recovery processes. Unlike most of VM's business operations, these recovery processes seem to work very efficiently for VM, sometimes ultimately resulting in the customer receiving defaults entered to their credit history and contact from debt collectors.
Unless you have given your 30 days notice to VM, you are still 'in contract' with VM and you move to a rolling 30 days once outside your minimum term.
There is a convoluted process of 'final billing' when you leave VM so it is also wise to keep and direct debits in place until that leaving process is fully concluded.
If you have made no progress in resolving your billing issues with VM, your next step would be a formal complaint to VM first of all
https://www.virginmedia.com/help/complaints
This is likely to result in a gobbledegook 'resolution' but is a required formality before escalating to Ombudsman Services for arbitration
https://www.ombudsman-services.org/
