Poor mtn service

Good day, I took out a contract with mtn in january online, they told me I have a 10 days cooling off period which I cancelled my contract before the 10days was up due to my device been very slow, i then was told I should phone In the contact centre give the reference of my cancelation which I did, I also requested a refund because I was billed for the device from the 16th of January but i only received the device on the 25th of January and I got billed the full amount of R310, from January up until now they are tying to debit me R6033 for the cancelation fee which I was told in February that will be waved out, and I am only getting charged unpaid fees, and I still never get my refund, pathetic service from mtn