Liberty *****ing my money after policy cancellation

I tried to cancel my life insurance policy in March this year. After many emails back and forth, the surrender value was finally paid out - but no confirmation that my policy was cancelled. Emails to this effect were ignored.

In April Liberty debited my account. In May an increased debit order from Liberty goes through! When I queried it, they mention that the policy is no longer active, and they want to reimburse me. The email requires a certain document to be completed and submitted. But there's no document attached to the email. After pointing it out, they just send the same email again - no attachments!

I just want the debit orders to stop! I want confirmation in writing that this policy is cancelled, and the debit order is cancelled! Taking my money for a service I cancelled is *****ING!