to repeat, you need to look at the original loan documents, specificially th eprovisions regarding assignment of the loan and whether the lender has authority to make changes to the terms and conditions of the loan.
I'd also look at the language concerning the "grace period" -- is it a term of the loan or is it just a matter of custom?
if it simply says the payment is due on the first but no penalty will attach for a late payment until the 15th...well, the lender can start "reminding" the borrower that the payment is due/overdue on the 3rd.
I think we're going to see more of that as credit markets tighten.
FYI on credit cards -- since those are revolving charge accounts with an expiration period, when the card expires you're likely to see new terms and conditions if you choose to renew the card. Cheshire Figment, the credit card companies wanted to keep your business, so they waived the fee and adopted the terms the original issuer gave you. but in the future, as you renew those cards...well, credit markets being what they are these days, you may have to accept less favorable terms on your acards in the future.