From my questions with customer service all you need to do is go to the home page at visible.com or the Visible app and select the plan you want and a new SIM card will be sent to you for the new plan you select. I am waiting to switch until they make us to save money since it is cheaper staying on the party pay.
One other thing I should point out is I don't think I have had any luck with the app and there is a problem with visible.com also erroring out when I am on my Overview page and click the button under "A better network is waiting" and I click on the "see new plans button" and when I select the plan I want it errors out. But, to get around that if I click the drop down menu for plans at the top and select check our plans, click bring my phone, click the check phone compatibility button, select your phones software(either iOS or Android) and run your phone then select the plan you want if phone is compatible you can proceed to order it that way. FYI, if you have an android phone it would be my suggestion to get a physical SIM card because from what I have read eSIM doesn't work on android and on iPhone it is hit or miss.
