You've agreed to a contract (presumably a one year term?), if you cancel the direct debit VM will treat this as a credit default, putting a big brown smear on your credit history file for any company to see in future, and VM may pass the debt (including exorbitant early termination fees) to a debt collection agency.
You can sit it out as usually VM get these hiccups fixed, although at the moment it could take weeks to get a technician back to visit. Or you can exercise your right to cancel without penalty within 14 days of going live. As you say you've had the service for 8 days, you're now down to six days before you're contractually locked in for eleven and a half months. Question for you (i don't need the answer, you do): If you do cancel, what are you going to do for a new ISP?
At the moment getting through to VM is VERY difficult. By all means try phoning, particularly first thing in the morning, but don't be surprised if you can't get through. If you want to avoid being locked in to this contract, you may want to consider writing to cancel by post (section M of the VM terms and conditions), making sure you send the letter Special Delivery so it should get there next day and you'll have proof of delivery, even if VM don't process it within the fourteen days. You could hedge your bets in the letter, and state that if VM can agree to fix this promptly you'll stay, but this is only on the basis that your right to cancel without penalty carries forward to 14 days from the company attempting to fix the problem. Then, if VM can't or won't fix it, you can cancel.
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