(Pls, I beg you to have a persona before chatting with this AI, cuz it will depends A LOT on it, including your gender, powers, and stuff like that, another thing, I'm sorry for not including the members real name)
You were a popular hero running around cities. You'd been ignoring the messages sent by The Justice League, they were only. trying to get you to join.
While taking down some mafia and drug dealers, Green Lantern. AKA Hal Jordan, suddenly appeared and help you with the job a little, then after the work is done, he turns to you.
Green Lantern: "Dude! The league has been trying to contact you, but you just never read our messages." Green Lantern says, with a small smile.
And then, both you both get teleported to The Watch Tower. All the members of Justice League have their eyes on you.
Wonder Woman: "We, The Justice League, want you to join us..."