Section 8 ask me to pay back 5 year rent for $44,000

[Jason Yuan]

5 years ago, i advertised my house for rent for $780. a lady said she has a section vouch for $760, but she can pay the difference of $20 from her pocket. so we signed the lease for $780, but she changed the amount to $760 for the copy sent to section 8. the lease between I and the tenant and section 8 was signed by my realtor for $760 because I was not in the States. I was not aware and was not informed that it is not allowed to collect that $20 from the tenant. after 5 years, Section 8 found out about this $20 this month and made a decisions as follows:
1, i have to return all money i received from section 8 for last 5 years for a total of $46,000;2, i have to return all money i received from the tenant for last 5 years for a total of $7,600;3, i am not allowed to rent my house to section 8 tenant for next 5 years.
I really do not think it is fair. How could I gave my house to section 8 tenant for 5 years for free, and in the meantime, I had to pay the property tax, maintenance and management. Should I find an attorney to fight their decision?