Ignoring client emails

Miway confused me when they offered me insurance verbally over the phone. Thus within 3 days ( well within the 7 day cooling off period) I emailed them to ask them to cancel my debit order as their insurance was actually two separate amounts, the sum of which, which far exceeded what I was paying my existing insurer. They have ignored my emailed cancellation instruction as well as my verbal cancellation instructions. Where do I go to get this debit order cancelled?