A top up should be available from within the VeWorld App as manual and recurring automatic transfer to do the top up. It should be a card that works in most European countries and that you can add the card in the digital wallet of the phone. So you can use the real card or the digital version stored within the phone.
It makes sense to foresee dApp integration options with for example Greencart so you can also claim the receipt back into the Greencart dApp.