Home Depot's Usurious Interest Rate of 68% APR

I have a Home Depot credit card and have had it for years. We seldom owe much on it and use it as a convenience and for an ocassional large purchase like the garden shed we purchased recently for $500. The Home Depot bill is due on the 18th of each month. Last month I paid it online through my bank (Bank of America) on this due date and the bank put it through that same day, according to them. However, Home Depot did not post it until the NEXT DAY and charged me a $39 late fee. OK, I'll accept that -- I should know better than pay on the due date. BUT THAT'S NOT THE ISSUE. Home Depot also RAISED MY INTEREST RATE TO AN ANNUAL APR of 68%. That is NOT a typo - it's not 18% or 28% or even 38% ... yes, it is SIXTY EIGHT PERCENT APR. Is that even legal? How can Home Depot possibly get away with that? (BTW - I have a credit rating above 725 so that's not the issue). I haven't even called to complain because I do not think I could keep myself from going thru the phone at the poor innocent person on the other end of the line who would have no authority to make it go away!

This 68% interest rate is usurious and borders on criminal. I cannot fathom how Home Depot's management can do this in all good conscience.