A ban is a possibly , you have to realistic about that. It’s not just a few days overstay , it’s months. Maybe speak to a reputable agent (check reviews online) for help. Get something arranged ASAP, avoid the police as the punishment will be much stronger if you don’t go to immigration yourself.
Pack all your belongings up ready to be sent home. Avoid the police.
I wouldn’t recommend trying to sneak over border crossing like a comment suggested , there is 99.9% chance you will be caught and then you will be in bigger mess than now.
Go to local immigration ASAP and explain the situation with all evidence of the agency who scammed you and point out to them it’s your first time in Thailand (they should be able to confirm this on the system / via passport stamps). You really need to take a thai speaking translator with you to understand fully.
Be prepared to pay a big fine and face a ban, but if you are very lucky and plead innocence you may get away with just a fine.