IRRESPONSIBLE LENDING

I HAVE AN ARRANGEMENT WITH GETBUCKS AND I HAVE PAID MORE THAN THE ORIGINAL AMOUNT AND I AM TOLD THAT THERE IS INTEREST EACH TIME THE ORIGINAL AMOUNT IS NOT SETTLED AND THEN WHATS THE USE OF AN ARRANGEMENT WHY DO I HAVE TO PAY IT IF THE LOAN WONT BE SETTLED AS SOON AS THE ORIGINAL AMOUNT IS PAID AND WHY IS THE INTEREST NOT COMMUNICATED WILL I EVER PAY THE ****** LOAN AM SO ****ED OFF