Bad service from cell c

For the last few days ive tried to cancel my contract with cell c on multiple time ive spoke to the cancelations department and multiple personnel everytime they tell me I've failed the security questions to my own account and then promise that someone will phone me back to sort it out but to no avail With another contract the previous year that i also cancelled due to bad service they were only supposed to charge me for 10days pro rata but ended up charging me for the whole month and it was a hige strugle to get them to refund the money. None of the customers care personal want to identify themself when speaking to a customer over the phone