TL;DR Can a retailer back out of their own Terms and Conditions because I used a discount code that I did not have explicit authorisation to use?
Full Details I found a discount code online for a gift card provider. With this particular gift card, one can send it off to the provider to 'redeem the balance', minus a fee. This allowed me to buy the cards and return them and get back more than I paid. (For example, suppose you get 20% off a £100 card, ie £20 reduction, and the redemption fee is £10. You make a profit of £10.)
When I made the purchase, I entered the discount code, and it was accepted. I then ticked the Terms and Conditions box---the Ts and Cs make no reference to discount codes (but do say that I can redeem the money for the fee). Upon my attempted redemption, the provider said that they would not be proceeding with the redemption, but rather refunding what I paid originally; their argument is that I didn't have authorisation to use that discount code, and that it was intended for a specific company (to which I have no connections), and that this discount code came with additional Ts and Cs, which include not passing the code onto a third party and that all cards are sold on a non-return basis. (The code was readily available on multiple voucher websites.)
I responded that I had not agreed to any of these Ts and Cs, but rather the ones I had agreed to made no reference to exceptions to the redemption clause (and no reference at all to discount codes).
They have now replied with the following statement.
Pending further legal advice we will be making a full refund [as you requested] to you less any card charges as this matter is dragging on.
We must make you aware however that we may be contacting you soon regarding the refund should our legal advisors advise us to do so. This may include contacting the police for the unauthorised use of a Corporate Discount Code.
We would advise that you refrain, in the future, from using Discount Codes not received directly from ourselves as you are now aware that they are not designed for the use of an individual for profit.
I had no knowledge that it was a corporate code, and were that the case my order should have been declined. Is the comment about "contacting the police for the unauthorised use of a Corporate Discount Code" just trying to scare me, or legally am I at fault?
If necessary I can provide the name of the company and a link to their Ts and Cs, but I would rather keep it anonymous if possible