Billed for a contract phone that was never delivered

on the 3rd of August 2017 i app**** for an online contract at MTN of a package that cost R 429.99, the package included a Samsung galaxy A5 2017 phone with data, minutes and sms. I was told that once i receive my delivery the contract will be activated and they will also charge pro-rata of when the contract was activated as my debit order was scheduled for the 25th of each month. I told the person who was helping me that i would like to use my number as a contract and they said it was fine. then the next day my number was ported to contract and i was surprised that my contract has been activated before the delivery of the devise was complete, i called MTN and ask why the ported my number before i had received the phone and signed the subscriber agreement form then they told me that the devise will arrive within 2-10 days. i waited to receive a call from MTN about the delivery and i never received a call from them, then on the 25th of August i was billed R525 that was debited on my account and since i have tried to call them to cancel this ******* contract which was never completed and i am not getting any assistance. i want my number to be taken back to prepaid seeing that MTN never delivered on their agreement and now my life in inconvenienced because i wanted a phone now i cant open another contract until this one is cancelled.