Oppo mobile phone can't receive SMS. What happened?

The number of SMS center is incorrect, and the cell phone signal is unstable.

1. The number of the SMS center is incorrect. Short message center number refers to the short message service center that the mobile phone needs to connect when sending and receiving short messages. If this number is set incorrectly, you cannot send or receive SMS successfully.

2. The cell phone signal is unstable. If the cell phone signal is unstable, you can't send or receive SMS successfully.