Refusing to assist with profile.

Hi, I am so frustrated and disappointed with the processes at this bureau, I want to dispute information on my credit profile that is not reflecting correctly on my profile. I have proof of payments on my side, I just want a email address to send them to. However transunion say I must contact the credit provider to send them the information. The creditors says that the debt was sold to third party and I am unable to get ahold of them.