Welcome to the community and thanks for posting. Sorry to hear you keep getting logged out when trying to upgrade via your online account.
I see you've also posted here regarding the website. As enlli mentioned, we have had one or two issues with the site recently. Are you still having trouble with this?
If you're still having problems then it could be an issue linked to your account. This means you'd have to call in to get it processed but it's really just a guess at this point. Aside from calling, you can also speak to our web chat team.