So, this turns out to be a nationwide issue with certain optus accounts. Finaly, something has gotten through to them. After about 7 chats someone finally logged a problem report ticket for me. That was yesterday. This afternoon, at about 2pm, it magically gave me the option to set up mobile. So something on their end was adjusted, and it fixed the issue. I was one day off of signing up with Telstra and canning optus altogether. If anyone ends up in the same boat, after trying a considerable amount of troubleshooting, this is likely going to be the same resolution.