I had the same problem with Montgomery Wards. I had my card when they actually had stores and I filed bankrupcy in 1994. I sent copies of my bankruptcy to all 3 credit agencies and Transunion and Equifax took it off but Experian did not. I would dispute it and still they would say that based upon information from Montgomery Wards they would not take it off. I would call Experian and asked them to tell me what Montgomery Wards actually had and they would pull my fill and say nothing was annotated but still they would not take it off.
Montgomery Wards would actually change the amount each time it neared the 7 years that would drop it off my file. I had to go to an attorney and they said they were violating my consumer rights.
You may have to go to an attorney and ask them to write a letter to both Montgomery Wards and the credit agency that will not take it off.
Good Luck!