Have given my iPhone to wife and have another iPhone I swapped my SIM card and the wife has a sim only deal but we still seem to be linked How can I be separated from my old phone

It sounds like both phones have the same Apple ID. It is a bad idea to share Apple IDs between different people. You should log OUT of the shared Apple ID on her phone, and she should get her own Apple ID.

Note: edited to change on to OUT

Now that you’ve separated Apple IDs you can link them to share purchases, calendars and other data selectively by setting up Family Sharing→What is Family Sharing? - Apple Support