The first thing to do, is to cut up or burn that credit card. Then call the issuer and close the account. That will prevent any probability of you even being tempted to try and use it again.
Calling the credit card companies is the first thing I would do, tell them your predicament and see what kind of options they can offer in the situation.
If you're just completely underwater, your cards are maxed and realistically don't have the means to get these balances paid down or paid off, even over time, you could consult a bankruptcy attorney and see if that could be an option for your situation.
Have you heard of either the Snowball or Avalanche approach to paying off your debt?? You can either begin to pay off your card with the highest balance or with the highest interest rate. Either one will lead you on a path toward a debt free lifestyle! Check out one article I found helpful here: https://turbo.intuit.com/blog/debt/debt-repayment-strategy-81/
Also, has anyone else had experience with one of these approaches? Did it help improve your credit score like mine did?