Oppo didn't back up the SMS, how to get it back?

You can try the following methods to deal with it:

1. If you have turned on the cloud backup function before deleting the notifications/messages in the Messages APP, you will try to recover the deleted notifications/messages by using the methods of cloud backup and data recovery.

2. If you don't turn on the cloud backup function before deleting the notifications/messages in the Info application, the deleted notifications/messages will not be retrieved.

Tips:

In order to avoid the inconvenience caused by data loss, it is recommended that you back up important data on your mobile phone regularly.