Can I cancel my I-765 application for replacement of OPT EAD card, if I got my old card back?

Yes, you can cancel your new application when you receive the receipt of filing. That will give you a case number with which you can correspond with U.S.C.I.S. I do note, however, that U.S.C.I.S. will not return your filing fee. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.