My question involves collection proceedings in the State of: California
I recently missed making a payment for the first time in about 20 years on a credit card. I paid it one week late when I realized I had missed it. I do not have a problem with paying a late charge, although I don't think it is good business practice to charge it the same day the payment is due.
My problem is that they classified it as a "purchase" then turned around and charged me interest on that late fee. Is it legal to classify a late charge as a purchase and charge interest on it? I've been in the debt collection business for 17 years, mostly with mortgages, and I have never heard of charging interest on late charges.

