Former staff member left iPhone 5s which is linked to his Apple ID. Sign in to iCloud pops up all the time. Find My Phone feature was on. I've asked him to remove this phone from Find My Phone which he did. Here is instructions how he did it https://support.apple.com/kb/ph2702?locale=en_US
Now, although he removed iphone from his iCloud account, the phone still asks to sign in to his iCloud. I cannot reset it, erase the data and anything else.
So the question is does removing iPhone from "Find my Phone" remotely (online) logs off from iCloud? How can I sign of from his iCloud and reset the phone? Erase it?