Manager at Call Centre not contacting me to resolve the interest charged on my Account

My daughter is a secondary card holder on my Edgars Account. Last year August she made a purchase at Edgars Trade Route Mall. The Consultant confirmed with my daughter that the purchase would be on 6 month interest free, I have been a customer for years at Edgars with a 6 month interest free option. I was charged 17.5% interest on an amount of about R375, I called the Call Centre several times to dispute the interest charge. The last two Consultants I spoke to was Charne and Noluvuweya who confirmed that the Manager Zenaria will contact me. To date I have not been contacted and the interest is continually being charged to my Account. I have been a loyal Customer for many years with not a single payment in arrears. I am so disappointed with the service, :-(