Since they keep engaging with you, time to turn the tables on them. The next time they ask you a question, ask them one. Research what you think might work with them.
Like, "Doesn't it bother you that the Watchtower has predicted the end so many times, and have been wrong every time?
Did you know that the Watchtower end time chronology was based on the wrong date?
They have basically been doing the same to you, time to fight back. They will probably get uncomfortable and drop it and won't do that again.