No delivery of sim card

On 23 April 2015 one of the sales people phoned me and I agreed on a 2gig data contract. Wednesday (06/05/2015) it has been 2 weeks and I have not received anything. I phoned Mondo mobile and they advised that the order was never fully processed. I told the lady that I want to cancel everything and that I am no longer interested in the contract. On Thursday evening I received a sms to say that my device has been invoiced. I again then phoned Mondo mobile on Friday (08/05/2015) and the sales lady advised me that their system is off line and she cant check anything for me. But when the courier company comes to deliver the sim card I must not take it and send it back. I would like something in writing to confirm my cancellation and that their will be no money deducted from my account. Can someone please assist me whose system is online and working.