Unauthorised debit order

A debit order went off my account and it is the first time I hear about this company and didn't even know that there is a company like this that exist. I don't have any contract with this company what's so ever. I don't understand someone comes into an account and debit an account that no loan money was credited into. I've been trying to call this company for the whole day and they AVR is busy tell me the caller number that I am and the estimated hold time. They don't even answer the phone to be able to explain who gave them the authority to debit my account.