Poor service at MTN

Two weeks ago I received a call from one of their consultants, wanting to assist me with upgrading my contract. We concluded on everything, a week later I get another call from a different consultant saying she also wants to assist with the upgrade because the previous transaction was not concluded. We go through the same process again, a couple of days later, I call to check on the status of the delivery, I'm told the transaction was not concluded because there's no stock available. I then ask them to cancel the whole process, I'll just go to one of their branches. Today I get to their store ans I'm told there's nothing they can do because there's a block on the system.