System upgrade, service downgrade.

I am disappointed in MTN's service delivery and regret taking out a cellphone contract with this service provider. My contract is for 36 months. Upon enquiry in January of this year I was told I'd be able to upgrade in March, by two different store attendants. When I called customer service and spoke to retentions however, I was told I could only upgrade in April. I resolved to wait until April seeing that it was only a few weeks away. In April on the exact date I was told I could upgrade when I tried to do it online I received a message saying my number is not a contract cellphone number. Once again I called their customer services. I was then told that due to their system being changed I unfortunately could only upgrade in June. This call was cut and unfortunately no one explained why this was so. I called again and this time someone told me I could only upgrade end of July/early August. Keep in mind my contract expires in October. No explanation or apology for all the misinformation was given. I was also told that if I wanted the upgrade now it would cost me an extra R800. I would like an explanation as to why I was told I could upgrade when in fact I couldn't and also why I keep getting a different story from different individuals working for MTN. At this point I just want to be done with MTN but even cancelling would cost me more than it would to see it through.