How can I get a code back after an error in redeeming it occurred?

Hello, this afternoon I tried to redeem a 14 days free xbox live code (in bundle with my Xbox One X) using my account on the official xbox site.

I was showed a warning that the code corresponds to Office 365 Home or Office 365 Enterprise (both written in red, with the option to choose one of them), with the clear indication (in yellow) that if the code was intended for the Xbox I should use it on
the console.

But when I followed this guidance, all I got was a message that it has already been used.

I then used a second code I had (in bundle with a new gamepad) and everything went OK.

Later on I got in touch with Xbox Support so to have explanations on what happened and to ask for a replacing working code.

After a chat with a very professional and competent support agentit came out that the fisrst code had been actually redeemed on the first attempt and then overwritten by the second one...

Honestly, I think that this is lack of proper communication, if it was valid since the beginning why on earth I was showed those messages?

And, to tell the truth, I simply followed the advice, without checking if I was already in the "grace period" (why would I? The system gave me clear indications on how to proceed).

How this issue could be fixed?

:)