Getting support calls after theft of an iPhone

My mother's Iphone got stolen a couple of days ago. That same day we reported the phone as stolen (can't block the icloud account since she does not remember her password, and it's using an old and inactive email)

We're both getting calls from "Apple Customer Support" (in spanish since we're from Perú) from a 5*******4 number (New London, OH, USA). The bot is asking for the 4 digit passcode, so we can trace the phone even while turned off.

Is this a trick from the thieves? a scam for me to enter the passcode? I keep hanging up because it seems fishy, but it being from the same US numbers makes me wonder.

Should I enter an invalid code or just let it be.

Thanks.

[Edited by Moderator]