No one from giffgaff would call your wife so it's definitely a scam, unless it was voicemail asking for her voicemail pin that she may have setup? Other than that it's definitely not giffgaff.
Very strange all round. Hard to understand why someone posing as giffgaff asking for a pin that doesn't exist? Have you told anyone at giffgaff about this yet/
giffgaff don`t call anyone asking for pin numbers or anything else
i must admit i had a call from an educator once.a case of mistaken identity though
Yes be careful as it's definitely a scam.
Never had a call like that myself fortunately.