Rudeness from a manager at flight center travel

Fight centre had a promotion that they were running with Samsung. They said the voucher can be used within 30 days of departure to the holiday destination. I wanted to book for the 28 August to the 31 August 2018. I was told that I should have given them full 30 days to do this booking. Meghan Thomas that was assisting me was of very good assistance. I spoke to Andrian Van Rusburg from Flight Centre who gave me so much attitude. Telling me that he bought Samsung on board and he is the one who is the project manager. What I wanted to clear with him is that why was this explicitly stated to me when I was given the voucher and for him to take ownership of his mistake. Instead he went on and on about that's are the terms and the conditions not wanting to accept any responsibility in this.