Track your package alert from Amazon.
Clicked on the button which took me to the Amazon page offering e-mail or mobile phone login.
They have my mobile number so I duly entered it. Not recognised came back. Not sure if I tried again or just went to e-mail and logged in normally.
A few hours later I got a phone message from Zap refunds offering to help me claim for a non existent PPI loan!
AFAIK my mobile number is not generally available.