Bait and switch. It’s my favorite because you set them up to fall hard.
Chances are you already know at least one thing your narc can’t say no to. Something they need or want that will immediately get them excited or motivated. Call them and say you’re going to make that happen. Get them as excited as you can. Let their selfish imagination run wild for a while. Let them get all dreamy. Compliment them too.
Set up a time and place to meet them, but don’t go.
Let them wait. Let them start blowing up your phone. After they get really angry, respond and say you’ll be there in 20 minutes. make up an excuse that sounds believable.
Wait until 25 minutes have gone by. Tell them your’re just about to arrive. You’re pulling up right now (even though you’re really somewhere else safe, relaxing without their drama)
Don’t respond after that. Turn off your phone or block their number. This is the hardest part to do, but it will absolutely drive them batshit crazy, for days and possibly months. They will be obsessed but unable to do anything about it.
Be careful however, because their mask will come off and it will be very ugly.