I have gone to the icloud.com web site there is no trace of the old user id.
That sounds as though it's the same account with a changed address. If so...
The only solution is to change your Apple ID back to its previous state with Apple at My Apple ID using your current password, you don’t need access to this address if it’s previously been used with your Apple ID, once you have saved these details enter the password as requested on your device and then turn off "find my phone" and delete the account from your device.
You should then change your Apple ID back to its current state, save it once again and then log back in using your current Apple ID. Finally, turn "find my phone" back on once again.
This article provides more information about Activation Lock.