Going over your existing credit limit could mean:
Your card is declined when you try to pay with it
Your provider could freeze the card until you’ve paid off some of the balance
You’ll be charged a fee for breaking your agreed credit limit
If you have a 0% credit card, you’ll most likely lose the interest-free period and be charged a much higher interest rate
If you continually overspend, your provider could ask you to pay back the full balance and even close your account
You’ll damage your credit score.