I just got a call from a girl in the canteen. I'm nervous. I want to ask how to send a text message without being rude.

You should be generous. Don't be afraid, be tactful, but be direct. Don't be such a mother-in-law Don't ask her out to play in a hurry. Tell her your name generously in the text message. If she has seen you in the canteen, tell her that you remember who I am and who I am. Let her think that you are a generous and concise person, and don't say anything else. Let her tell you from the beginning.