I met it! He usually sends me text messages to chat, but never calls to chat. Why?

I chatted by SMS because I had time to organize the language, but I called him. When you ask him a question, you can't react so quickly. I can't answer you silently. . What's more, the phone will be very embarrassing, and I can't find a topic at the moment. I probably put my foot in my mouth when I'm nervous. I don't choose what to say.