In Australia most retailers discount specific items for “members”. Being a member is free but you need to sign up with your contact details. They will give you a card but no one carries a million cards so cashier’s just ask for your phone number.

The Australian Communications and Media Authority administers phone numbers in Australia and they publish a list of phone numbers which may not be used by telco’s and are reserved for the exclusive use in TV shows, films, and creative works.

I made a note of one of the numbers in my phone, and provide that when asked. Loads of other people are doing this so the number is always registered at every shop.

The conversation usually goes:

• cashier: are you a club member?
• me: yes.
• cashier: what’s your number ?
• me: <ACMA number>
• cashier: oh. wow. there seems to be hundreds of people with this number. what’s your name?
• me: oh really? who’s there?
• cashier: uh, nigel, john, luke…
• me: I’m Luke.

I’ve been doing this on a weekly basis since reading about it in another thread (on reddit) a few years ago. I’ve never encountered a problem and I’ve received thousands of dollars in discounts. I would’ve gotten those discounts anyway but would’ve had to sign up with my personal number in order to receive them.