Being disabled does not exempt someone from being contacted by a debt collector (or a creditor) about an outstanding debt. However, if the debt collector sues a disabled person over a debt and obtains a court judgment against that individual as a result, the debt collector cannot garnish (take) any federal disability payments the disabled person may be receiving. However, the debt collector could collect on the judgment by going after other assets he or she owns.
If you need more specific information, I urge you to contact a consumer law attorney in your area. I also recommend that you consider purchasing a copy of the e-book about dealing with debt collectors and consumers' debt collection rights that I co-authored with Gerri Detweiler. It's available as a download on this site. You can read the first chapter of Debt Collection Answers online for free.