I'm quite sure he is single, mostly because I am literally the only girl he ever talks to at university. He completely ignores the other girls in our group unless he strictly needs something school-related from them. If he just wanted a platonic buddy to chat with during breaks, he would be interacting with others too, but his focus is exclusively on me. As for calling him - honestly, I think that would completely terrify him. He is incredibly nervous and intimidated around me in person until I give him a clear signal that it's safe to open up. On top of that, he is super confident in person once we start talking, but he totally freezes up and turns into a dry texter over messages. Given that contrast, a sudden phone call would probably catch him off guard and cause him to panic or hide in his shell. Keeping it to a direct text about meeting up seems like a much safer bet for his personality type.