MTN UPGRADE

According to Mtn I have been due for a upgrade since mid December. Even got a sms to say if I don't do it by the time my contract expires they will up my fees anyway. They have a company calling me several times a day when I can't answer my phone to offer me a upgrade... Luckily I decided to rather go in store and a kind employee informed me I will be charged a R400 fee if I upgrade before the actual expiry date of my contrac!!! So mtn is hounding me to upgrade before my expiry date so that I must pay them extra?!? But does not make this clear upfront. I find that very dishonest. Wonder how many people u have conned into paying.