Unauthorised increase

I've been an account holder with Edgars since 2014 and never had an issue paying my account. When I opened the account I requested a 6 months interest free payment plan. I was advised that I can only qualify for this after 12 months by the lady at the new accounts dept. in Edgars Gateway. A year later I enquired about this and was told that I cannot go from 12 - 6 months (I ignored this). I was requested twice to authorise an increase on my amount to purchase and on both occasions I had instructed the cashier to state that I DO NOT want the increase. I was asked to sign at the back of a till slip which declines the increase. Since then my total purchase amount has increased from R4500 to R7000. I never requested this, why was it increased? Why was I misled by your new accounts person? I am really disappointed with Edgars and I want this rectified!