if I dont have access to my iphone, how am I supposed to get a code to deregister imessage?

The code will be texted to your cell phone of whatever type you have now.

Deregister iMessage on your iPhone or online - Apple Support

Then contact Apple Support directly:

Contact - Official Apple Support

I need to deregister iMessage and don't have access to iPhone anymore I've been through all the steps the confirmation code is not coming to new phone

This is not the case