Refund for not activated sim

[lrina]

Good afternoon! I bought a SIM card online and couldn't activate it because I entered a non-Italian number in my details, and I couldn’t receive a confirmation code. I visited the branch in person, where told me I could legally get a refund within 40 days and that I could do so on the website. I want a refund for an unactivated SIM card. How do I do this?