If you no longer want to ingest contacts from your Google account, Microsoft account, or Local Address Book and remove all un-touched contacts, you can remove the account(s) by clicking on Settings and looking under the Integration header.
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Select the account that you want to remove and tap Remove All Authorizations at the bottom of the screen. 

Removing the authorization will prompt you to Keep imported contacts or Delete imported contacts. 

Note: If you choose the Delete imported contacts option, UpHabit will only delete un-touched contacts. Contacts that have reminders, tags and notes set will not be deleted.