Marlin Leasing Marlin Leasing posts payments AFTER the due date in order to charge late fees Internet

Twice now Marlin Leasing has charged us a late fee (significant late fee) for 'paying our lease late' when in fact the payment was mailed and received by Marlin before the actual due date.  The first time they indicated on our bill that the payment was posted (that means received they say) on the 2nd ... our payment is due the 1st ... therefore they claimed our payment was late and they charged us a late fee of $57.00!  Yes, $57.00 on a payment of $382.00.  Upon further investigation we found out that our check (payment) cleared OUR bank on the 1st.  How is it that Marlin Leasing cashed the check and had it back through ours on the 1st when they claim they posted it on the 2nd?  It took us WEEKS to get the late fee reversed even when they were faced with the unrefutable evidence.  Well, it's now happened again .... January 1st's payment arrived in their lock box on December 31st as indicated by the tracking number from USPS. (Ever since the first incident we've been sending our payments priority mail with tracking because we don't trust them).  That payment didn't get posted until January 4th so now they are charging us another $57.00 late fee.

If that practice is not illegal I don't know how.  It is at the very minimum unethical.  Obviously I am refusing to pay that late fee.  Don't know how that will turn out yet but I am wondering how many customers they have scammed out of money this way in the past and plan on scamming into the future.  It's a heck of a revenue stream for them.  There has to be someway out there to determine if this practice is acceptable or punishable.