Student Discount don't work - Portugal

[trid9mendes]

Hi everyone,
I'm trying to get my premium student subscription but my credit card doesn't be accepted. I already know that I have to submit a document that proves that I'm a college student but I don't know how to send it to Spotify. Can you help me? I'm from Portugal so I can't use the USA system to subscribe but I know that Portugal is an accepted country since April 2017.

Thank you!