Bad service

I'm writing to express my disappointment with the service I've received from Sanlam Insure. I had a policy with them and requested cancellation last month, asking them not to debit my account this month. However, as soon as my salary was deposited, they debited the premium despite my cancellation request. I had signed and submitted the cancellation form to the email address they provided, but now they're claiming they can't locate my submission. When I asked for a refund, they told me I wouldn't be eligible. I'm confused as to why they're taking further action when I've clearly cancelled my policy.

Could you please assist me with this matter and advise on the next steps I can take?