Clarifying - as soon as phone is turned on I am asked to log on to ICloud. I know that Apple ID and Password is correct. But it is not accepted. So - I am stuck cannot do anything with the phone
If you are trying to activate your phone it is asking for the ID and password that were originally used to activate it. If you are not the original owner, you will have to contact the original owner and either get the ID and password, or have them erase the phone and remove it from their account as explained here: Find My iPhone Activation Lock: Removing a device from a previous owner’s account.
Have you signed up for iCloud?
did you verify your iCloud account email address?
Clarifying - as soon as phone is turned on I am asked to log on to ICloud.
