A birthday card and a Red Bull ruined my Target credit limit

My husband and I own a small restaurant in Chicago. Whenever it's a servers birthday, I'll run across the street and grab a card for all of the staff to sign. I use the RedCard for even the smallest purchases because you get 5% discount, so why not. But because Target has the most ridiculous autopay structure for their RedCard, I typically just pay the card off once I get home. Well, I forgot. This purchase led to a balance of $7 that I missed the payment and was hit with a late fee 3x the balance, and my credit limit went from $13,000 to $300.
I WENT FROM BEING ABLE TO BUY HALF THE STORE TO A 20in TV ..OVER $7. Yes I called, the late fee was removed (cute) but nothing was done about my limit.