Problem is the contacts have already been synced to your device, so only removing the accounts would delete them automatically. HOWEVER, since you already turned off sync for all additional accounts but still left sync on to your main account, you can just re-force the sync. Open your App Manager, find the Contacts app, and wipe data (Just note that this will delete ALL Contacts, including those not backed up to a cloud account! So make sure you have your information backed up elsewhere before doing that!). Now just wait. The system will automatically re-sync your main account (because the Sync Contacts option is enabled) and leave your other accounts offline.
05-24-2018 12:36 PM