Beware MTN early upgrade fees policy change without notifying customer

We have about 10 business phones with MTN for over 15 years and have never had any problems with upgrading the contracts. We have always upgraded in the 21st month of the contract with no problems. A few months ago we were notified that 4 of the contracts were due for a upgrade so we went ahead with the upgrade , on our next months bill we now had an early upgrade fee on the 4 number , we were never told about a early upgrade fee when the upgrade was offered to us and when I contacted customer support they said , the policy had changed and there are no free upgrades from the 21st month anymore, ( We were never told about this) I sent a email to the MTN complaints department and never got a response. So it looks like MTN can just change their policies without notifying the customers and the customer just has to pay. It also looks like they don't respond to any hellopeter posts so it looks like I will just be writing this as a warning to other MTN customers that MTN can just put unexpected charges on your account and there is nothing you can do about it . Beware MTN shady practices