For me, I use gift cards I receive as a test of the person that gave it. Someone I consider a collegue but not friend giving me a gift card to a place I like instantly makes me think they value me more than I thought. Person I consider a friend gives me a gift card instead of a gift, depending on the occasion, makes me think they like me, but can’t be bothered to put too much effort in, or are just doing because they feel obligated.
I don’t know what kinds of packets WiFi calling sends, but I would assume a public IP would be in there somewhere and, at least from a law enforcement perspective I can’t imagine it would be too hard to get the address tied to it.