homechoice hidden chargers

home choice is making ripping me off , when i got the order the order my installment say R296,48 which was higher than the installment I saw on the website but it meant sense cause the statement say including facility fee but now , i just received a statement that says R622,21 after i paid the R300 installment by the way , when I called the very useless staff told me that the installment is due to change monthly , when i took out the credit accounted with you i took it out based on the amounted that i saw on website , that what i could afford not knowing the is more hidden chargers , you ripping people off mx