How do I upgrade my Linkedin subscription from Premier to Advanced if the Advanced subscription is not listed?

I have Linkedin Premium through iTunes. I want to upgrade to Advanced because I need sales navigator features that only come with Advanced. On the iPhone, I cannot find any way to upgrade the subscription. Under iPhone/Subscriptions/Manage Subscription, you can see from the attachments that I am missing any option to upgrade. From my desktop, when I click on "Upgrade your plan", I get the message Upgrade "Sorry, this option is unavailable" which you can see from the attached pic. It indicates that I have to do this on my phone. Please tell me what to do so I can upgrade my account.