It seems your complaint (this version, since some of dates have changed since last wrote) is that you were told "end of the year" (December 31) and they refused to allow you to use it on December 21.

It was wrong of them to use non-specific language, like this. "End of year" was likely a shortcut for "some time in December." I agree, that's wrong.

However, that doesn't erase the fact that you had a full year to use the voucher and didn't. And once it expired, it expired.

Are you saying that you want a reinstatement of the voucher simply because the person said "end of the year" but really meant "December 14"? Is that your argument?

Please understand, but the way, that you've also made a similar mistake. In your original letter, which was dated in January, you said "today." But NOW "today" means "December 21." The fact that YOU were none-too-careful about your use of "today" shows that anyone can make the mistake of being imprecise in language.

What matters is the rules for vouchers, which Delta is consistent with.

Might I ask why a frequent traveler, such as yourself, didn't get to use the voucher in the 365 days it was active?