Unauthorised Debit Order-New Client

I took out a car insurance with you guys yesterday. I did the whole application online on your website. I choose my debit order to start on the 15th April because I'm currently with another Insurance company and they already debited me for March. I woke up this morning to you guys debiting my account, lucky my bank ask for my authorisation before a new debit order can be approved. I declined your debit order because I didn't have any agreement with you guys to take a debit order today. Honestly I feel I should just cancel with you guys cos I forsee problems already. If this is what you do to your clients, then you very unprofessional and I don't want to associate myself with such company. I'm very disappointed in your brand.