I got a very simple idea when I was recharging my mobile using the normal way, scratching a card to get a secret code and either calling recharging automated service or requesting a shorthand like in Vodafone *858*secretcode#
I suggest adding the shorthand substituted with the secret code as a QR code!
Then when I scratch the card I get the QR code as an alternative way to recharge besides the code for manual recharging.
The motivation is that most of phones now have built-in QR readers or it can be installed as a third-part application, which will quickly translates the QR code to the correspondent code and you can quickly call it!
Vodafone Egypt Example:
The shorthanded code to charge with secret code *858*12345678901234#
The Generated QR code:
What do you think?