It is a common misconception that if you are making any payments on a debt, the creditor cannot attempt to collect money in any other way (such as by suing you).
Without an agreement regarding repayment, such as an agreement that the creditor will accept $250 per month payments and not try to collect otherwise, then the creditor can take any collection action it deems appropriate.
Any payments not paid pursuant to an agreement with the creditor are simply voluntary payments on a debt. That does not stop the creditor from suing you (and ultimately garnishing your wages, etc.).