The fact you were "told" that financial aid would pay for your education and the fact that on your enrollment form you selected financial aid as the only form of payment does not prove that you don't owe any money. It appears that you received financial aid from The Student Loan Corporation so you need to direct your complaint to them. You also need to produce signed documentation that states that there would be absolutely no out-of-pocket expenses required to be paid by you.

The University of Phoenix Online is a very expensive school and is designed for working professionals to earn degrees while continuing with their full time careers. I have never heard of anyone getting 100% financial aid to attend this school.

The bottom line is the burden of proof lies with you.