John Lewis giftcards balance was used by others who I don't know

[The GodMother]

You stated the gift cards allows you to by products in the store the gift card is named for. 

Now as the non food items l stated about are in the store then it would be assumed by some that these things are able to be brought using a gift card. While you did not say everything you also did not state that there might be exceptions. 

[stones1229]

As an experienced giftcard purchaser, let me explain.

The retailers do not allow customers to buy a giftcard by using giftcard, of course you can use cash to pay for it with no problem.

 

But they are not technically forbidden it, which means, if the cashier/manager is not very clear about this rule, I can buy it without problem. If the Cashier says no, then I will be refused to do it.

 

But now, I can buy the giftcard by using self check out machine, so it is no problem anyway, even they are not allowed.