Unauthorised Debits

I have been with Outsurance a number of years. Now, I have sold my car and bought a new car and I contacted Outsurance to cahnge the necessary details.

I have 2 major issues:

A pro-rata amount has now been deducted from my bank account on 16th Aug. No authorisation was given telephonically. In fact, the agent did not even mention that this would happen. Thus no consent was given and after speaking to another agent this morning, it seems nothing will be done about this unauthorised debit.

Secondly, after asking the agrnt this morning what amount will be debited from my account at the end of Aug, he stated it would be my full premium. How is this possible if I have already paid my old car's insurance pro-rata yesterday and I will only be driving the new car for about 15 days? How then can Outsurance charge me for a full month's insurance?

I want answers.