nightmare with billing account

accounting and billing problem, i took out an online contact with Telkom October 2017 , the contact was for R139 per month , 11Gig ,this is 5gig anytime DATA and 5 night surfer. to my surprise my account only show that i only have 500MB and that i an i paying for the extra data usage and that they will not short my account out. this morning i spoke to Ntombi Zonke and she clearly told me that i'm liable for all the charges ,because i use the DATA ,she then refuse to supply me with the Complaints departments details and advise that she will refer matter to her manager Lungi Cele then she will refer the matter to complaints. I then called again and i spoke to a gentleman that was so confuse he did not understand what he was talking about told me that i have a contact for 20G and that the account is fine. its clear that staff at Telkom dont know what they doing and dont understand the products. He then told me that the package was a promotion and will have to pay charges. i want telkom to rectify the billing error or i need to cancel this contract. account no: ********** 84 , i just need to cancel this contract ,please i need to cancel this