Someone is signing for me without my permission - how do I stop this?

I had to sign a document for a business. I added my signature to the document - today I recieved automatic emails that I "signed" two other documents. I never signed them, they somehow used my signature to sign the documents. How do I turn off this feature and how do I remove my signature? I dont know what happened.  I dont know if they saved my signature to their business account or what. I am going to flag it for reported abuse but in the mean time is there anything I can do on my side to make sure they never use my signature again? In all instances ,even the time I did sign, it says:

My name

My email

Role: Signer

Authentication: None

Delivery: Email

Identity check: None