Launch VZAccess Manager. From the Windows desktop, navigate: Start > All Programs (Programs) > VZAccess Manager. With Windows 10, click Start > Apps icon (located in the top-left corner) > All apps (located in the bottom-left corner) > VZAccess Manager.
If presented, enter the PIN then click OK. The default PIN is 1111.
From the TXT Messaging tab, click Delete / Delete All. If needed, ensure the desired message(s) is / are selected.