Buying with debit cards

I hope that you will beable to
advise us about using Saudi Net cards [debit cards] when buying things
that we need from the stores. These cards are used in the following
manner: when the amount of the purchase has been added up, for example 150
riyaals, the card is given to the vendor and he passes (“swipes”) it
through a machine that he has in his store. The value of the purchase is
then taken instantly, by transferring the amount from the purchaser’s
account to the vendor’s account in the same instant, i.e., before the
buyer leaves the shop.