ToysRus say "10% discount to first time online purchase", but do not give the discount.

I purchased goods over a thousand rands ONLINE from ToysRus today. I completed the subscription, and submitted it (it asked for my name, and my child's name). It said 10 % off your first time online purchases. Next, I chose my products and made payment. Whilst doing payment, i was the screen asking for Discount coupon code. I tried several times to click on it, to enter code, or activate it, but it was frozen and didnt allow me to enter code). I then went on to make payment thinking that my discount would be given in my total. I later checked my email, (no discount came through. no code was sent) and saw that my goods were ready for delivery. I emailled and sent whatsapp messages to Toyrus, asking about my discount, (and sending them the screenshot of my subscription), but they are now finding excuses for their frozen screen and telling me that my goods are already discounted, that my purchases are only R300, and that they sent the code. I have checked all my emails. there are no discounts sent to me . They are finding all sorts of excuses not to discount me, by now telling me T and C applies... Yet they cannot accept that their system froze at the time.