As another colleague noted, it is very common for colleges to place a hold on a student's ability to register for classes when the student has outstanding debt owed to the school. In addition, it's been my experience that the school generally places the onus on the student to stay informed of their financial obligations to the school.
That having been said, you might consider speaking with the Bursar's Office to see if there are any options that may help you here. For instance, some colleges offer emergency loans to cover these expenses, though these loans generally have a pretty short repayment term. There may be other student aid options - federal loans, PLUS loans, grants, etc. - to help bridge the financial gap and keep you in school.
Best of luck!
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You got to pay the bill. Hard to get around this. Maybe talk with the financial manger and work a payment plan if it was their mistake.