Upgrade with hidden costs!!

I did an upgrade online for one of my numbers. The upgrade is for a sim only and was done online. After successfully upgrading, I received an invoice that shows I'm still have to pay for an device - IT ONLY SHOWS DEVICE ON THE INVOICE and not what device. When I phoned MTN and waited and incredible 15 minutes 46 seconds and the slow system that MTN has, I was told by the operator that I still have to pay for the old handset until JULY!!!. No where was I informed when I did the upgrade online that I will still be liable for the device, no where on any communication was I informed beforehand that this will be the case. I've been with MTN for 22 years now and this is the most ridiculous treatment I've received from MTN. I'm going to start and move my numbers to Vodacom.