Why is sending and receiving SMS delayed by Unicom's mobile phone?

There may be the following reasons for the delay in sending and receiving short messages: 1. The network system is busy, I suggest you try again another day; 2. Because of the mobile phone, you can restart the mobile phone or change the mobile phone test; 3. Long downtime or out of service area; 4.SMS inbox and outbox are full. Please clean them up and try again. 5. The mobile phone has been stopped, so it is recommended to pay for it and start it again. The above reasons are still unresolved after being eliminated, please contact the manual customer service for handling.