How to completely delete the SMS record of Apple's mobile phone

The information storage of IOS devices is divided into two places; In-phone and icloud cloud

1: In the phone memory, enter SMS to delete.

2: iCloud synchronization is closed. This is backed up in the cloud according to the apple id, and it will log in to the device with the apple id step by step. Delete Method Settings -I Cloud- Backup-Cloud Backup Off

3. Delete in ICloud, log in to Apple iCloud official website, log in to your account and delete the short message saved in the cloud in the message.