I am a co-signer of a loan for my son. He is paying the normal monthly payments and I am making extra payments towards the principal. I have requested that they apply XXXX % of the extra payment to principal only and if they can not agree to that, to return my check. They applied my first payment of XXXX correctly but the second payment of XXXX on XXXX/XXXX/15 they took XXXX and applied it to interest ( even though my son 's payments are current ). I faxed them an inquiry on XXXX/XXXX/15, no response. On XXXX/XXXX/15 I emailed them through their own website requesting they reverse the XXXX and put it onto principal. To date, they have not responded.