If you have been unable to pay your debt back for some time, your creditors may seek legal action against you to collect that debt. Usually, when you miss a payment, your creditors will they start with phone calls, then letters, or e-mails, and they get more aggressive.
After some time, they will start a lawsuit and you will know by receiving a summons and complaint. If you receive a summons and complaint, do not ignore it like a phone call or regular letter!