Poor service from Service Provider

In March this year I app**** for an Iphone contract with Istore online. The application took long to be finalised due to the lockdown. Finally, in the last week of April I recieved my phone, and during that time I was no longer interested in it. To my surprise within a week of recieving the device, the first debit order went off. The first week of May, I approached Menlyn Istore to return the device & ultimately cancel the contract. I spoke to Christopher Barnard who requested me to send a mail confirming that I've returned the device. I left the store thinking that I'm nearly done. Then I sent a mail to MTN customer care enquiring about the process of cancelling my contract. After numerous emails & poor feedback, I'm still struggling to get this contract cancelled. I've been taken from pillar to post, the last mail I recieved from them, they gave me a contact number to call *** which I did & couldn't get through, as I don't have an MTN number. I need assistance to get this contract cancelled, kind regards