Increase in payment

<p>We signed a contract with HIP Houseing under the impression it would help us be able to afford our very first house. Each month the repayment increases and has nothing to do with the intrest rate as that is on its own. we recieve an invoice every month for additional R5000 above what our payment is for. What is going on? we cant even contact anyone as the line goes dead and no one replys on emails. I want answers.</p>