Cancel Online & Telephone Upgrade Order

I try now to upgrade for last 4 weeks without any success. I first try through the MTN App and then I do it via the telephone without any success. I went in to the friendly MTN Store which are able to assist but there are a pending upgrade and they not able to assist till this upgrade order are deleted. I phone the number holding for a while just that they take my number and that they will call me back to cancel the order. I'm still wait for the return call. I just want to cancel this order that I can proceed with my upgrade through the MTN store. I will never use the app or online or phone to upgrade again.