Denial & Appeals: Mo Division of Employment Security

The State of Missouri wants me to repay unemployment benefits, which I have no intention of doing because by law they can't garnish pension checks, my only source of income. Also because it was the Division's fault to approve benefits to begin with, then realizing and apologizing for the mistake (which I do not agree with it, my claim was valid) and now asking me to repay more money than they paid me.
What is the statute of limitations or how long will they harass me or any other action they may take in trying to make me repay?
Thanks,
Maurizio

Denial & Appeals: Mo Division of Employment Security