Service is up to nothing

I upgraded One of my phone numbers, they sent the device and by accendent sent an additional phone too. So Cell C loaded 2 contracts on my name.

Then 2 days later I sent both phones back and cancelled the contract as I wast happy.( The phones werent even opened)

It took them 2 months to cancel the contracts and now they are still askinv me to pay the account or they will suspend my number??

No one has been able to resolve this and I have been phoning at least every second day for the last 2 months.