Please assist with canceling a upgrade, i have not received a device and have requested MTN to cancel the upgrade, i upgraded in March and delivery was not received. Please assist in reversing the upgrade.

In March i have upgraded for a contract with MTN, seven days later i requested them to cancel the upgrade. They promised but a month later they continued to deduct on my account while i haven't even received the device. I have phoned MTN and sent them emails several times but they kept on transferring me from one department to the other. The most painful parts is the fact that im paying for a device that i haven't received. I phone them almost every day but no one is able to reverse the upgrade i have also requested them to cancel the debit order but none of my requests have been attended.