Not honoring promotion as advertised

My letter to the MD:

"Dear Mrs. Mandi Samson: In response to your Black Friday Promotion on November 24, 2017, I purchased return tickets for my wife and I to travel from Durban to Windhoek on 21 March 2018 and return on 9 April 2018 (Blacked out dates: 23 Mar- 8 Apr). The ticket numbers are ***-********* & ***-*********x. While making the booking using Travelstart the indicative cost of R3777.29 per ticket (excluding travel agent rates) were calculated which we assumed would be adjusted to R2500 as stipulated on your promotion. On 30 November 2017 the full amount (R3777.29 (2x)) left our bank account.

We have conformed to all the terms and conditions set out on the promotional flyer and therefore petition from you a refund in the amount of R2 554.58 (two-thousand-five-hundred and fifty-four rand and fifty-eight cents) to honor the promotion. It has been over xx weeks since our inquiry into this matter and we trust this can be settled soon. If you have any questions, please contact me at (+27) *** *** ***x.

We would really appreciate your help to resolve this matter."

Air Namibia responded that my travels are within the blacked out period (which it's not), that the ticket class is W and not G (something I have no control over) and that I did not follow this up on the same day as when the booking was made. Therefore do not qualify for the promo.