Assign Existing Line to Another Existing Phone

[Dr_Z]

What is the most economical way to reassign an existing Verizon phone number to another existing iPhone already on my family plan? It looks like I can't avoid a fee, but would like to reduce it as much as possible ($20 through the app verses $40 in store?) and the exact details for a do-it-yourself option are not fully clear. It also looks like I will need a new SIM card since one iPhone is 5G capable and the other is not.

For clarification, I am ordering a new iPhone for one line, then plan to take that previous iPhone and give it to another family member. Their oldest iPhone will then be taken off the account. 

[vzw_customer_support]

Hello Dr-Z. We want to make sure you have all the information you need when it comes to moving devices around for your account. Activating an existing Verizon device on an existing Verizon phone number can be done free of charge. Here is a link with the steps to Activate/Switch devices: https://www.verizon.com/support/swap-devices-faqs/ -Tanisha

[mama23dogs]

Move the Sim card. The Sim card contains the phone number. 
If you need to add a new line, you can do that online. Activate the new Sim card in the older phone that you plan on using on that line.