I sent pdl co a letter on to adjust the date they will debit my accoun

I sent pdl co a letter on to adjust the date they will debit my account since my HR office sent us a memo that our payday will be officially the a later date instead the fixed date (a copy of the memo was sent as well). They refused to acknowledge that based on their correspondence with me. I tried to call them 3 times and waited 15 minutes each time without anyone answering the phone. I have paid them $440 on a $350 loan. What can I do for now? Thanks.