Upgrading Internet to unlimited but keeping TV CableCards...

I am trying to upgrade my Internet from 800Mbps to 1 Gig unlimited.  When I try to do it myself on the website I get a message after I submit the order that I must call or chat with Xfinity since it cannot be processed.  I think it might have to do that I still have cablecards.  I know they are officially not supported anymore and that once you lose access, it is very hard or impossible to get them working again.  So I don't really want to do the chat-thing because they often don't even know what cablecards are.  I have my own equipment, but the Xfinity gateway is free so was thinking of use that in bridge mode with my router, since my modem doesn't support 1 Gig speed apparently.  I tried to put the order in using my own equipement and also with the gateway, but both couldn't get through.  I have the "Popular TV" package, which doesn't exist anymore, so maybe that's why it failed too...  I just want 1 Gig unlimited internet, and keep my TV plan the same since I am paranoid that I will lose cablecard access.  Can someone help or advise here?  Thanks.