i have 3 iphones on 1 icloud account, all phone calls that are made and called in show up on all three phones. How can we stop this

We have 2 iPhone 6 and 1 iPhone 6s. All three are all up to date with updates, put every single phone call that is either made on any of the phones, or received on any of these phone show up on each phone. For some reason with the last update this is what happened and we can not figure out how to stop this.