TRUWORTHS MESSED UP MY ACCOUNT BECAUSE THEY'RE ***********

Truworths messed up my account due to no fault of mine and now it's affecting my credit score. Have been trying to get them to rectify their mistake but keep hitting a brick wall!! Now it's costing me airtime to contact them everytime because of their mistake and still they can't fix it. I had a flawless perfect account untill someone there messed it up. I WANT MY ACCOUNT FIXED!! Their call centre is useless waited over 35 minutes till my airtime ran out and their whatsapp is even worse! I paid up my account. I had a 6 month cellphone plan and a 12 month clothing plan. I paid up the balance on the account and then purchased a clothing item off R550 on 12 months. Somehow the R550 was split over the 6 month cellphone plan and the 12 month clothing plan resulting in a balance on the cellphone plan which should be 0.00. Then I get a statement saying my instalment on the R550 is R306.94!!!!! Because Truworths magically created a balance on 6 months cellphone plan when there shouldn't be one I am required to pay interest on 6 months AND 12 months one R550 clothing item so apparently that is why my instalment is R306.94 on a R550 balance!! Which is totally insane. I have asked them numerace times to recalculate my instalment and fix my 6 month cellphone plan balance to 0.00. I have spoken to over 7 different agents none was helpful except one that said he could see that a mistake was made and will sent an urgent request to their accounts dept to look into it...2 months later...NOTHING!! The other agents just tells me I must pay what they ask there is nothing wrong with my account. I'm livid and at my wits end with Truworths because noe I'm getting messages that my account is overdue and it will affect my credit score. You messed up my account now it's affecting my credit score FIX MY ACCOUNT!!