You are correct, IN is NOT a community property state.
Did your DH have insurance to take care of this medical bill ? Who's insurance coverage was it, yours or his ?
What type of medical bill - dr's office or hospital ?
Who signed to be the responsible party to pay the bill ?
If it was not your insurance, and you didn't sign any papers for his treatment, then YOU are NOT responsible for HIS medical debt.
Calling you on a cell phone is a violation of the FDCPA. You can send them a cease and desist telling them not to contact you by phone.
"Knowledge is Power - use it as you see fit !
I am not a lawyer or a member of the legal profession. My advice is based on research and experience, my own and others, some who practice law. You decide for yourself what actions you do or do not take from my advice.