To buy a phone from Visible sign into your account and hover over shop at the top and click shop all phones on the drop down list. Find the phone you want and add it to the shopping and finish the checkout process.
If you are not financing through affirm you can buy straight from Apple, make sure to buy the unlocked version of the phone you are buying.
Another FYI, any phone purchased through Visible is locked to them for 60 days. It needs to be used on the account it was purchased under for 60 consecutive days before it unlocks and can be ported elsewhere if you decide to leave.
There is no need to change plans in order to buy a phone, it isn't necessary. You can change plans at any time with or without the purchase of a phone.
Hope this answers your questions.
