There are several options that allow you to restore your contacts, and undo any recent changes.
Restore your Google Contacts:
Your contacts are automatically backed up by Google. So if you ever need to restore your contacts to an earlier state, it's very easy to do as long as your contacts were previously stored in Google. Follow these steps to restore your contacts:
- Go to https://contacts.google.com
- Find the settings (gear) icon at the top right, select it, and go to "Undo Changes." Proceed to restore your Google contacts to an earlier state.
- Next, open the Contacts Sync app and sync once again, to restore the same contacts on your iPhone
Restore your iCloud Contacts:
If your contacts were previously stored in iCloud, you can easily restore these contacts as well.
- From your computer, log into iCloud.com
- Go to Settings > Restore Contacts
- Then restore your contacts to a date & time when your contacts had not been deleted. Then sync again with this app. Now your contacts should be restored both on Google and iPhone.
Restore from your device backup:
You can also restore one of your backups made by the Contacts Sync app. To do so, go to Contacts Sync > Contacts > Backups, select the desired backup, and proceed to restore it.