Cancel policy and Reverse over deduction

i have a bondability life cover with Nedbank, i took it against the house that i bought through EFC, the house that was frist covered with this policy was sold and now i want to cancel the insurance, Nedbank make it difficult for me to cancel, though i wrote emails and communications through the telephones but they still deduct from my bank account. i reversed last month s deduction now they deducted R2278 which is tripple the premium that i know. i need them to cancel that policy and refund my R2278 that was deducted on 2 August 2020