i received a Summon (Sum-100) for a debt collection. However, I am suffering from an identity theft. What processes must be done to be take off debt?

If this debt isn't yours, you'll have to respond to the summons, and go to court.  If the amount is significant, I'd recommend hiring a lawyer.

Once you deny that it's your debt, the plaintiff will have to prove that you and not somebody else did this in your name.  Since this is a civil case, they don't have to prove it beyond a reasonable doubt, but they still have to prove it;  if they have an application with a signature, you'll have an opportunity to show that the signature isn't yours.