No upgrade for there fault

I am refused a upgrade because vodacom overcharged by R2500 TWICE. Now i need to upgrade my phone and they downgraded me to the lowest package possible. My average spend per month at vodacom is R2200 and this is the pathetic way they treat a loyal customer of over 15years!!! <br> <br> My upgrade was due in december which means i have paid for my device in full but yet im still being charged for the device on top of my current contract, so im probably going to get treated even worse now that i have complained about this as well.