I'm struggling here whether to send a message or call my boss for leave.

Call and send messages. If the boss doesn't see it, it will be embarrassing if you don't reply. Besides, calling is more respectful. Text messages will make people think that you are not asking for leave, just tell them that you can get the answer by calling directly. If no one answers the phone, he may be busy, so send the message again. If you don't reply for a long time, you can call again. If there are too many, don't call again. That's about it.