Wrong invoice sent and amount given

I phoned Telkom last month round the 25.08.2015 to find out what my amount is to pay for the month of July, and then I was told my account was R512 and some cents, and this amount also showed on my invoice I received via email. So I went and I paid the amount which I rounded off to an amount of R520.00. Now Telkom came back to me saying I owe them another R500.08 as this is the wrong amount, and when I went to check on my invoice the amount they calculated was wrong. But like every other person when you go to PNP or checkers and you see a price on the shelve and when you go to the counter and the price is more than what you saw on the shelf then they fix it and you pay the amount you saw or was told to pay.<br> <br> So now Telkom is going to cut my line as I did not pay my account due to this error and I want to sort it before I pay the account, I phoned them last week Thursday 03.09.2015 and spoke to the night team leader Sibongile or I think that's her name and she then told me she will go and listen to the calls where they said I must pay R512. the would've phoned me back and I'm still waiting no call received. so unhappy.