Discovery vehicle insurance

I cancelled my vehicle insurance with Discovery last year in September but they never cancelled my debit order and only stopped it in March this year. We have been contacting them for the last six months without much success as every time the financial department promise to reimburse me, but we only managed to get 20% back. It’s a nightmare trying to contact them, and the financial department just seems to not respond at all. Very disappointed to say the least in this group.