Hi @sherwood1948,
Welcome back to our Community Forums! Thank you for your post and for your query.
You don't need to use the O2 SIM card if you don't want, however, one of the Volt package benefits is that we boost your data on your O2 SIM card. You can read more about the Volt Benefits on our website.
Please let us know if there's anything else we can do to help, we're happy to assist. 🙂
Thank you.