Can I put my iphone 6 sim card into a new SIM-free iphone 6S?

I want to get the iphone 6S but I currently have Iphone 6 with sprint.

If I get the SIM-FREE iphone from apple, can I just put my existing sim card onto the new phone without contacting sprint for activation?

Since Sprint is CDMA activation would likely have to come through them, not a SIM. So you could probably get away with it