In order to delete calls, please follow these instructions:
If on Android:
On Talkatone, tap on the Calls icon, select the contact, tap on the arrow showing on the single call, tap on the Android menu button, and tap on Clear Calls.
If on iOS:
On Talkatone, tap on the Calls icon, swipe left on a contact to delete the call record with that contact.
NOTE: Once you delete the messages/calls log, you won't be able to retrieve this information.