unauthorised debit

I signed up for car insurance with dial direct, one hour or so later I called to change the primary driver listed on the policy to my daughter instead of me, the lady said my daughter has her licence for too short a while and therefore could not be insured. I asked for the policy to be cancelled, the lady cancelled the policy and ensured me that no debits will go out. I signed up with another company on the same day. Now One week later dial direct debits my account for a full one month's premium despite assuring me that this would not happen. The procedure for a refund is not easy and not immediate. How can this lady lie like this, I need a reversal of this debit order with immediate effect.