Along with the contact centre saying it was ok .
Actually they didn't say it was "ok".
Had you asked them this specific question:
Can I use my staff discount to buy a gift card, and then get another staff discount when using the gift card?
Then you'd know what the answer would have been.
But instead you simply asked
Can I use my staff discount to buy a gift card?
Let's face it, you somehow wondered whether you could in effect use your staff discount twice for each purchase by buying gift cards to make your in store purchases as opposed to buying them normally and then receiving discounts.
Initially you probably thought that there's no chance staff could buy gift cards as it would be easy to abuse, and I bet you couldn't believe your luck when you were told that you could. So off you went to buy your first gift card with your staff discount, and then at a later date you used the gift card and claimed your staff discount again. Because I can guarantee that you'd never have been able to buy a gift card and then use that gift card that very same day to buy an item in store, and you know that full well. The staff member would have pulled you up. But then again you'd have just made sure someone different served you.
Where the company policy loophole can be closed easily is simply not allow staff to purchase gift cards.
It doesn't even make any rational sense that you'd need to buy gift cards, because in the cases you've specified, you've been told by your dad and other friends and family what they wanted. As opposed to giving them the gift card and then letting them buy it.
As I don't trust anyone, especially people on the internet I'd say I think your friends and family knew the loophole that you were abusing and thought "Lovely Jubbley...even more % off".
Unfortunately ignorance is not going to save you, people on the internet can see it a mile off, as I'm sure you're employer will too.
I just hope the extra discount was worth it. All depends on how much you relied on your job for income.
It's all about risk vs reward, for example you don't go and rob an off-licence with a shot gun as the few hundred pounds is not worth the risk of punishment you'd receive. And equally I wouldn't risk losing my job for tens of pounds. You go all out to make the reward greater than the risk.
You took the risk for supposedly a small sum, and you're going to lose your job.
Reminds me of someone I used to work with that lost his job, he was taking part exchanges from customers behind the books. He'd offer x amount for a customers part exchange, and just not declare it on the invoice and then sell the cars privately making a pretty hefty mark up. It caught up with him when a customer left an item in their car and then came into the showroom on the salesmans day off wanting to collect it. There was no record of the part exchange and as you can imagine the sales manager went livid once he caught on to what was happening.
Unfortunately the motor industry is a small world, and he's pretty much got ZERO chance of getting a job as a car salesman (or in the motor trade again)
In your case as it's I'm assuming a small part time retail job, you can and will probably anyway remove them from C.V and end up in a completely different job.