misleading clients, with their interest free story

worse experience when I first bought their products they told me it was interest free, few months later made a 10k deposit to their account, and missed that month's payment, and continued with my 700 installment, few months later they add interest on the account saying couse I missed a payment, they charged me 1700 for missing 700 payment after paying them 10000. this company is a rip-off