un fair treatment

I paid my instalment in April, it was not captured by getbucks and I complained. I was told to send bank statements and I did all they asked from me. it is July now and my payment has still not being sorted in the meanwhile they deducted again with interest and instead of closing the loan they added more interest so the loan can stay open. when I asked about this I was told to get phoned back and instead of a call I got tretend with legal action from them I do feel that this is not right and thy do not treat there clients right and I am very unhappy