Unauthorized debit order and forced insurance on me

I was dealing with Budget Insurance in July hoping i will manage over to them but their premium was higher than my current premium so i clearly wrote back to them that i will not be moving over i am happy with my insurance with outsurance. Come the first of September they debit my account and keep sending me messages about my missed premium. Cause my account had no money as i did not make provision for the debit order i incurred bank charges and i wrote to them that i did not want their insurance as my car is now double insured. On the 21st of September they have debited my account. I want my money back, please contact me.