Pretext is usually used as a noun. As a transitive verb you can say. pretexted, pretexting, pretexts, meaning to allege something as an excuse. Examples: He pretexted that he was at school when he was at a cafe He is pretexting that he is early when we know that he got up late It doesn't really sound right. I would use pretend rather than pretext.

Adding to Jura's answer, I suggest checking if native speakers actually would treat "pretext" (or any word) in such a way. I usually type my phrase into a search engine to see if someone else has written it that way before. It is technically possible to make "pretext" a verb, but your sentence may end up sounding clumsy or absurd, simply because native English speakers simply won't use it that way.

Thank you Jura & Peachey :)