A PIN is not required for transactions performed over the internet, phone or mail.
PIN is only applicable when you are physically present at the point-of-sale during the purchase or withdrawing cash from an ATM. There are some circumstances at the physical point-of-sale terminals when a PIN is not required to authorise a transaction, most commonly at contactless terminals for purchases under $100 and low value payments under $35.
There are no circumstances in which you should ever reveal your PIN when making a purchase via internet, phone or mail. For these purchases you will be asked to provide your card details and the security number on the reverse of the card. It is important to remember that the security code or CVV is notyour PIN nor should you make it your PIN.