User is retiring from job, apple id is tied to company email address, how to change email address of apple id without losing any data

User is retiring from job and their existing Apple id (signed into iCloud on the corporate device) is is tied to their present company email address. How can a person change the email address (aka apple id sign in name) without losing any data or purchases? FYI, In many some cases the respective Apple ID utilized in the Apple App store for purchases, is a personal Apple id, despite the Apple ID being used to actually sign into iCloud is a different Apple id tied to the person's company email address. Thanks