*****ulent debicheck approved

I've been sending numerous emails to 1Life for cancellation of a life policy I had done a quote for however no one has reverted back to me to confirm cancellation. The reason I want to cancel this is the debicheck that was approved without my consent and this to me is *****. How does 1Life approve a debicheck mandate on my behalf. I want this cancelled with immediate effect and I do not expect any deductions to go off, I'll hold 1Life liable for any bank charges!!!