Data transfer from iPhone

Do the procedure on the old XR. (Once you are happy ALL the data has transferred.)

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

Abemmy wrote:

transferred iphone xr data to new iphone 15 pro. both phones still work

You really copied the data from one phone to a new phone. You didn't move it, so I'm not sure what you're asking? It's not like taking a gallon of water and putting it a new bucket. Both phones would still work. If you don't want your data on the old phone, follow the procedures in the link Servant of Cats provided.

What is the question?

Ate you looking for the article on what to do before getting rid of the old phone?

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

Abemmy wrote:

I transferred the data from iPhone XR to iPhone 15. Both phones are still working. How do I stop the XR phone from working?

You open the link Servant of Cats provided and I already mentioned in my reply to you and you follow the directions in the link to fully erase the XR. Click on the Blue Word Link. Follow the directions.

Abemmy wrote:

I backed up with I cloud Is that all I have to do.

No. You need to wipe the old iPhone XR. Open the link provided. Follow the directions. If this it just too hard for you to do, go to an Apple Store and ask them to help you wipe the phone.