I like a girl, but she ignores me, so I can only send her a text message. What can I say to make him stop ignoring me?

You can try to send her one or two short messages every day (when she doesn't reply), not too much, and then keep talking about your interesting things today, care about her, and don't expect her to reply to you. If she is bored, you can insist that you don't send it, then please stop.

If she replies to you, your tone is not very enthusiastic. Don't send too many messages a day. Maybe she replied out of courtesy, so don't send it out suddenly when you think it's hope.