nag 'n brag - You whine about something you paid for. You get a freebie or

You whine about something you paid for. You get a freebie or a discount. Then you act like you're the best person ever and show off.

I complained about my coffee being weak, got a free latte, and now I tell everyone I'm the coffee king.

I yelled at my barista for not knowing my order, got a free cookie, and now I brag like I'm a barista boss.

I got charged extra for my sandwich, I screamed, got my money back, and now I say I'm the sandwich champion.