Unhappy customer

On June 2017 I have ordered curtains and bed sheets with home choice and I got my stuff in the same month, the sales consultant who was calling me we agreed with R140 payment monthly but on their system shows that my monthly instalment is R280 they than called me and told me I am in arrears. I was so furious because I didn't know about that amount then I decide to settle my account with them ,They told me my settlement amount isR1350. I paid that amount last year October2017. Than last week on 23-May-2018 they called me and said am in arrears of 289.69 and I have settle my account last year.