An unknown mobile phone number sent me a short message.

This is a malicious message. If you reply to this message, it will eliminate your phone bill. Or you have subscribed to a service. I often receive such messages, such as: "Hello! Long time no see, old classmate. Where are you developing now? I work in Jiangxi. It's nice here. Come and play sometime. I will receive you. Eat and live in my bag. Li ... "I don't know him at all. But he wrote this. I really thought I was one of my classmates. So I sent a short message back. Next month, I checked the mobile company and said what service I ordered. The telephone bill is higher than before. 50 yuan, I checked.