how do i deactivate my old phone. I still get messages on my old phone

Hello Deacones1,

If the cellular service is still active you'd want to contact your wireless carrier to cancel that.

If you've already transferred your SIM or cellular service to a new device, and you don't want to receive messages on the old device then you can either turn off Wi-Fi so the device no longer has an internet connection or turn off the iMessage service in Settings > Messages.

If you're getting rid of the old device, then you'll want to completely erase it to remove all data and account settings. Settings > General > Transfer or Reset iPhone > Erase All Content and Settings.

Here's a helpful guide for preparing to get rid of an old device: What to do before you sell, give away, or trade in your iPhone or iPad

Cheers!