I shall answer this allegation with the words of Ahmad(As) himself. Ahmad(As) states:
“This is a revealed new word which is not found in this form in the Qur’an or hadith or in any dictionary. It has been disclosed to me that it connotes [ya la sharik] [O You without an associate]. The purpose of this revelation is that no human being possesses a quality or a name or performs any action which is peculiar to Him and is not to be found in any other. That is why the qualities and the miracles of every Prophet are displayed, by way of reflection, by some of his selected followers who have a perfect spiritual relationship with him, lest the ignorant ones should hold a Prophet to be without an associate because of some uniqueness. To call a Prophet Yalash would amount to utter disbelief.”([Tohfah Golarhviyyah, p. 69 footnote) Yalash means without an Associate, so as a Sunni do you not believe Allah can be called that? Do not restrict Allah to 99 names. 99 Names are from the Quran but Allah has many more names and has been called more names by Muhammad(Saw) himself.