Changing my service

When I try to change my service online, the website does not load properly for me.  It only offers me to option to add mobile and not change anything else about my plan.  I have tried using the horrible AI assistance and it just directs me back to the page that does not load.  I have tried calling the support number and it just sends me a link to the page that does not load.  I NEED TO TALK TO A HUMAN PLEASEEEEEE