In order to delete messages/calls, please follow these instructions:
If on Android:
On Talkatone, tap on the Messages icon, select the contact, once the chat log is displayed tap the Android menu button, and tap on Clear messages/calls.
If you wish to delete individual messages, just hold your finger over the message you wish to delete for a few seconds. A red button should appear giving you the option to delete.
If on iOS:
In order to delete messages, please follow these instructions: Under messages, swipe left on a contact to delete all conversations with that contact, or open the conversation and swipe left to select individual messages to delete.
NOTE: Once you delete the messages/calls log, you won't be able to retrieve this information.