Three year old collection with unautorized inquiry

Can a collection agency, who has bought my almost three year old debt from another collector and issued a brand new date of debt on my report be allowed to perform a hard inquiry on my credit report? I called them and told them "here I am" and that I wanted to pay or negotiate to make both parties happy. After three months of having my debts they decide to inquire my credit report. They tell me they are fully within thier rights and will use other avenues to get their money. I told them that I will be notifying them by mail that I am not to be contacted at work or home but by mail only according to my rights. Please help me as to whether or not they can do this according to your knowledge.
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they are not allowed an unauthorized inquiry
call your or the state attorney general