How to back up iphone6s SMS?

Open the synchronization assistant software installed on your phone, and then log in to your account.

Click the "More" button in the upper right corner.

Then click the "SMS backup" item.

Then select the Backup to Network button.

Select the messages that need to be backed up according to their importance, and then click the "Backup" button below, and the system will automatically back up the selected network messages. (Keep the network open)

When you need to restore the SMS, click the "Restore to this machine" button below, then select the SMS to be restored, and click the "Restore" button below.