Translation:Wij zullen de politie gebeld hebben.
I see that Duo accepts sentences ending with "gebeld hebben" and "hebben gebeld", but I wonder if there's any difference of meaning between the two.
'Wij zullen de politie gebeld hebben'? We shall have called the police?
that should be okay especially if you are British. Here's an interesting website that breaks it down: http://www.grammar-monster.com/easily_confused/shall_will.htm