Over charged for more than 5 months and they couldn't care less

After upgrading my phone and selecting a new contract from the less than average Mtn store in Clearwater Mall I waited for ages for the contract to be activated only to find out that it wasn't done until I complained. Now after 5 months of constant complaints and emails explaining that the contract that was meant to cost R579 and is being billed at R692 I get told I need to prove that, that was the amount I am meant to pay even after sending the signed contract to numerous people in Mtn, my advise to anyone thinking of going to Mtn is don't!! You'll be ********** and sent from pillar to post just so they can keep milking you for more than you agreed to.