I can't send an Apple Gift card

I was trying to send a gift card from my account, which is feom Portugal, to another account, from the UK (I don't know if the region I am sending the gift card from or the region where I am sending to is of any importance). But when I have already chosen the amount of money the design and everything, I click BUY NOW and a message saying that that action couldn't be completed and to contact iTunes Store support. I searched for iTunes Store support and didn't find anything about ehat happened to me, so if anyone knows what should I do, I'd appreciate some help.

P.S. I am trying to do this from my iPhone 6 and my software version is 12.4.5