Truworths 3 pay account

I have a 3 oay account that i managed to get in order to build my credit score and the last time i used it recently and they phoned me saying i have an outstanding balance of x amount but when logging on online it was half the amount they said i have to pay. Now i havent had a chance to get to a store and neither did i ask for them to disturb me at work 25 times a day. Now its showing on my credit score that im in arrears but it hasnt even been the full 3 months outstanding only one month since there is confusion on the amount. This is pathetic and i hope that they could understand that one doesnt sit at home waiting for them to call. Now im just sitting with a issue breaking down my credit score. Thank you for lying truworths