Promo didn't apply

I was given a promotion that expire today on the 7th, i app**** the promo before i could order. Yesterday on the 6th of April at check out the promo was app**** but they deducted normal price excluding the promo discount. I queried for reversal of my funds and their response was that the promo applies to certain countries. What i do not understand is that it was not written on the email and the promo was active on the app but they didn't apply it when they debited my bill.