Treating one of your most loyal customers with such disregard

I want to cancel a data sim contract i took out on 16.05.2018 with MTN Direct. I want to do this while the contract is still within the cooling off period. Apparently my device, a Huawei Nova, is no compatible with a dual sim, as there is no settings to activate the sim in question.I have made at least 10 calls to ********** . Every single time that I call, I'm told that I need to speak to Kgabo Molokomme at the JHB branch. To date, I have heard nothing from him or his manager. Apparently all 3 agents I EVENTUALLY got through too , have sent an email to both, to contact me. STILL NOTHING. If Im going to be billed and have to run around anymore, Im sure I will lose the plot. i have been with MTN for the last 10years,thanks MTN for treating one of your most loyal customers with such disregard!!!!!