Is it legal for a collection agency to try to collect on a debt that was released in bankruptcy and then sold to the collection agency by the original creditor bank?

Legal or not, this happens every day. Inform the collection agency and the original lender that this was included in the bankruptcy. The collection agency may want to see proof but usually the original lender will call and request that - that particular account be sent back.

Make sure you get something in writing from the original lender--and that the collection agency REMOVES their account off your credit report--check your report 3 to 6 months later, to make sure this has been done. If you don't want to wait--send a copy of the signed letter on the lender's letterhead to all 3 collection agencies and wait for their response. Even though it will take about 30 days--this is the quickest way.