Can Hartford force me to file for Social Security Disability? Can they hold my benefit checks if I don't?

Hello. My name is Wanda. I have been out of work since 6/2011 and have had 2 back surgerys in the last 6 months. Still under Dr’s care, pain management and in a lot of pain if I try too much of anything. Now they think I may have some nerve damage and I received a call from the company I work for, which stated they could no longer keep me on the payroll and I was dismissed. Now Hartford has called and ask how I was doing. I told them the above, they sent me a letter giving me 21 day to show that I have files for Social Security Disability and that I check the be on the box that if I get retro I will pay them the lump sum… Also if I don’t file they will hold my benefit checks. Can they do this? Am I required to file for Social security? I am 55, not sure if or when I will be able to work, since I can’t sit nor stand for long periods of time.