You can contact the Ombudsman of the Department of Corrections and they can put a block on your phone number. It will block it so that no inmate in any Indiana state prison facility can contact you. I used to work in a prison and used to do this for people all the time.
Here is a link to the Ombudsman for Indiana.
http://www.in.gov/indcorrection/ombudsman.htm The phone number is at the top of the page.
They should be able to help you out or will at least be able to get you to the correct department.