Walden University Sent to collections on course I withdrew from online class Internet

I attended Walden for a year and had trouble with a class which brought my gpa to a 2.07. I repeatedly emailed financial aid if I was qualified for financial aid due to this low GPA and to please inform me before the deadline. I finally received a reply weeks later stating I was not but had loans and other options. I immediately informed Walden that I wanted to withdraw ASAP (stated this in an email inquiring that if I couldn't get the financial aid I needed to withdraw) and went about doing what needed to be done. Fast forward 9 months ago they sold the debt to a collection agency. I informed the agency of what happened and they asked if I was going to pay this bill so of course, I told them no. Well now they've reported me to the Credit bureaus and I plan to fight this every step of the way. What an unethical money hungry unprofessional institution. They don't care about their students or else they would handle these matters better. What makes them think a person qualifying for GOVERNMENT financial aid can pay over $2,000 for ONE class??? Run, don't walk away from these vultures.