A guy that likes my girlfriend keeps texting her at night. What should I do?

My girlfriend has been receiving text messages from a guy she went to school with, he had/has a crush on her and live in the same neighborhood. The 2 most recent text went; "you are still awake" this was at 3 a.m. in the morning, and the last one was; " Hey" "wyd", this was at 11pm when she just got off work. I trust her and she says she does not speak to him. He will most likely keep bothering.I am wondering, how should I proceed? I will update.
Asked Apr 01, 2017

TIP: If it's not your answer to this question, please click "Leave a Comment" button under the question to communicate with the question owner.