Yet another Mobile service provider milking money out of their customers as soon as you try and cancel your contract

I've had a contract with Telkom Mobile since April 2014, all the while very happy with the product and customer service, yet when I neared the end of my 24 month contract I decided that I no linger have use for this product and wish to cancel this contract on date of expiry of the 24 months, to avoid a month to month contract and payment. Unfortunately this invoked the usual dark side of what seems like, every mobile company that offers a phone or tablet contract, service of any kind was out the door. I phoned the customer care line where a very pleasant lady named, Lungile Zinhle Mdlalose, kindly offered me the help I needed, explained to me that I need to complete a form (which she immediately emailed to me) and send it to ***. I was very satisfied with her service and assistance and completed the form and emailed the form to the provided address, confident that this easy and effective process was in action and that my request will be handled. This was the 7th of March. We are in May now, I've received no confirmation that my contract has been cancelled, I've received 2 invoices with amounts completely different to the amount I signed for in my contract, the first of which is R712.73 (as apposed to the R297 I've been paying for the last 24 months) and the second, not deducted yet, an amount of R513. Ive mad 3 to 4 calls to the call center since and sent mails, but never receive a response on the status of action taken or that the contract has been cancelled yet. Really does feel like they're abusing my debit order and deliberately wasting time to milk me of as much money as they can before any action is taken. I would really appreciate it if my debit order and contract can be cancelled immediately and I be refunded for the money they've taken since April, as the sim was last active end of March when I removed it from my device under the impression that the contract would've been cancelled on date of expiry.