Poor service

I went to Edgars Menlyn to pay my installment on Saturday. When I received my installment it was more than R300 higher than the previous month. Customer care wasn't very supportive but eventually the rude lady on the telephone said that the installment increase was due to a late payment the previous month. I paid on the 7th the previous month and according to my knowledge payments should be made on or before the 7th of the month. The lady on the telephone was rude and not helpful. I'm considering closing my account. Never had this problems at Foschini.