My question involves collection proceedings in the State of: California

I was in an verbally abusive relationship where i was convinced that i had to cosign a loan for my ex. This was a loan to pay off his bills and get him a new laptop. We have been separated for over a year now and I am getting calls from the loan company that i need to pay because he has stopped answering the phone to them. I know that I signed the documents so I am being held liable but what actions can I take against him given the fact that none of the loan was for me? Please help!!!