Why do people always text when they call?

If the phone can't receive the call, directly enter the SMS call, indicating that the phone has set up call forwarding. If call forwarding is set, incoming calls will be forwarded according to the current setting;

Call forwarding generally includes power off or out of service area, transfer in case of busy, transfer all, etc.

If call forwarding is set, just cancel the call forwarding function directly. You can set it through the phone menu, and iPhone 5S can operate it through Settings-Phone-Call Forwarding.

I suggest you try it after the operation. If it still doesn't work, you can try another mobile phone if it's convenient, or contact local customer service to check the status of the mobile phone.