Collection account - not the primary account holder

I have received notice from a collection agency that a $69 bill is due from whenever my daughter moved from her apartment. My wife and I co-signed for the sublet (she was not the original leasee) for cleaning charges. When she moved in, we notified the complex about several items that were not up to cleanliness standards. It was noted in her file and my wife and I re cleaned the entire apartment. When she moved out, we asked for someone from the complex to have a walk through, but they kept making excuses as to why someone was not available for this. Ultimately, three months after she moved out, we got a letter from the collection agency about this cleaning charge, but not once was my daughter notified. When I asked why, I got nothing but a heated response that we are just as responsible as she is - fine, but what about the original lease signee? We made the issues known to the complex but no response. This really infuriates me as I have all but cursed these idiots out at the agency because of their willingness to show proof of notice to my daughter and if I paid the account to have it removed from my credit report. The apartment complex will no longer take my calls. Any suggestions?