A little help needed for a young entrepreneur!

I graduated 1 year ago and started my own business. Now my government is making me pay them because apparently I was working more than I should while completing my 3,5 year degree in 2,5 years! Now as a starting entrepreneur, I could use some help.

So there is a system in Finland, that you - as a student can get a monthly support payment from the government. But there is a working limit. So you can only get paid 600 euros a month, If you want that support payment, which is about 500 euros a month. Me as a responsible young student, did my calculations and worked while studying and earned the allowed amount in a year. But the employer made a mistake with the paycheck and paid me more than they should have. I returned the money, but the salarypayment department didn´t tell the government so they think I have made more money than I really am because they don´t have a record that I´ve returned the salary.

Eventhough I have the evidence that I actually have returned the salary, One man simply cannot fight the power of the government, so I have to pay. And this is were I could use a little help :)

Thank you!