Does your customer not have a registered Joyn card yet?
In that case, suggest he downloads the Joyn app on his smartphone. In the app, the customer can register his card. This way, he always carries his Joyn card with him, wherever he goes!
Does your customer not have a smartphone?
In that case, he can register the card in the Joyn app on your tablet or via the web page my.joyn.eu/card-registration.