Wrapping It Up
Sadly, you can’t deactivate any iPhone, iPad, or iPod Touch device created iCloud accounts, even if you don’t use them (or they were a previous owner’s account.) That’s because this maximum number is tied to the device itself–the hardware–rather than any one user. Any single device can ONLY create three iCloud accounts in its lifetime. And there is no way to change this or wipe the slate clean.
However, there are options to get new iCloud accounts. Instead of creating an iCloud account on your current device, set one up on a Mac or a friend’s/family member’s iOS device–you cannot do this via a Windows PC or Android device. Once you set-up that new iCloud account, just log in with your new Apple ID credentials on your device and you are good to go.