"I can't believe you put the mailroom boy's name on the wall." I think what you mean is that you can't believe yours was ever taken off.
باورم نميشه اسم اون "پسر دبيرخونه" روي ديواره. فکر کنم منظورت اينه که باورت نميشه اسم تو اصلاً برداشته شده.