Cancellation

My experience with Mtn is not a pleasant one I took a contract with Mtn in August September 2024 for an Iphone 13 which they said it will be around R799 but now they deduct around R2100 which I don't know how we arrived there the contract have 2 sim cards the other sim card they said I can cancel it anytime I want in December I've send email to cancel several agents responded to my email but to my surprise it is not cancelled. Yesterday one agent called me about they reward asking me how the contract is keeping me I've relayed my story to her she told me I should've called Mtn to cancel the contract not email I'm surprised because agents that I have communicated to on the email haven't told me that I'm truly disappointed in Mtn they don't even deserve my 1 star