I just bought a mobile phone, Huawei C88 12, and got a telecom card ~ and then I received a text message saying, "I'm using your mobile phone."

Generally, receiving this message means that this card has been set with the anti-theft function, that is, the person who has set the anti-theft function will send a text message to its associated number when changing the card, so you will receive this message, indicating that this card has been used before, and now it has been used after being invalidated, but the number with the anti-theft function has not changed, so you received this message.