Your mortgage provides for fines, penalties, interest and charges for delinquent payments. It is also likely that the matter was sent to an attorney and it is not unusual for the attorney to add $2,000.00 to $3,000.00 or more to the arrears in legal fees.
You need to have someone look at the numbers and your mortgage before a determination can be made as to whether or not these charges are unreasonable.
Disclaimer: This answer does not constitute legal advice. I am admitted in the States of New York, New Jersey and Massachusetts only and make no attempt to opine on matters of law that are not relevant to those three States. This advice is based on general principles of law that may or may not relate to your specific situation. Facts and laws change and these possible changes will affect the advice provided here. Consult an attorney in your locale before you act on any of this advice. You should not rely on this advice alone and nothing in these communications creates an attorney client relationship. The opinions expressed herein are those of the author only and the fact that he has worked as an Assistant District Attorney; State Supreme Court Clerk; Special Assistant United States Attorney (Hawaii); Assistant Cornell University Counsel or Judge Advocate, United States Marine Corps should not be relied upon to assume that these statements reflect the policy of these organizations.