I might be missing something here but just an hour ago I did a favour for a friend and took a card to a shop, gave them some money and they printed out a receipt with a multi digit number on it. I then typed * long number# into a keypad by the meter and it credited the money to the electricity meter. As far as I can see no telephone line is connected so how does that work? At no time other than at the shop did I need the card.