Mondo - please deliver

I have entered into a Telkom contract through Mondo last year (2018). I've had two sim cards (data and airtime) under this contract. Unfortunately I've lost both two sim cards and have been paying ever since for something I do not get the benefit of. I have contacted them and explained this and they told me that I must suspend the sim cards and do a sim swop. I did suspend the sim card numbers but are still invoiced for it every month. They told me that it is the only way and there is nothing they can do about it. I told them that I then have to cancel the contract seeing that I do not get any benefit, where after I was told me that I would also have to dock up cancellation fees. I am deeply disappointed and feel that I am being exploited and trapped in a contract of which I don't get any benefit from. I have recently reverse and stopped this debitorder but are getting threathening sms's from the supplier, if i don't pay the reversed debit order. I want them to provide me with new simcards, then I will be welcome to allow them to debit my account, seeing that I will pay for something that I'm getting the benefit of.