illegal debit orders

I must say, I am sick and tired about this SMV company or whatever they are. They have illegally been debiting my account since last year September and they not stopping. have been paying bank charges for them for months or having to do reversals but they still continuing. I don't know them, don't know what business are they in and have never heard of them except seeing their name on my bank statements. honestly, I can't go on like this, now I'm forced to change banks because of the unauthorised debit orders that goes through my account monthly and leaving me on a negative balance not forgetting - denting my account. Can Smv enterprise stop going through my account without my permission - that is fraud..