Make these adjustments on your work phone to unlink it from your personal iPhone:
Settings > Phone > Calls on Other Devices > toggle off Allow Calls on Other Devices
Settings > Messages > Send & Receive
Settings > FaceTime
Settings > (your name at the top) > iCloud > toggle off iCloud Drive
Settings > (your name at the top) > iCloud > Photos > toggle off iCloud Photos
Now calls, call history, messages, and FaceTime will be separated from each other.