We removed a Piezo Buzzer from the wall that the telephone line connected to it.  The previous owner was elderly so used it for amplification when the phone rang.  It had a horrible shrill sound when it rang so we took it off.  We've reconnected the wires but now can only receive incoming telephone calls we can't make outgoing calls.  We get a line disconnected signal which suggests we've connected the wrong wires.

We have a black cable with 4 wires
-yellow
-black
-white
-brown

And a white cable with 4 wires
-white
-red
-blue
-green

Which wires are supposed to be connected for the telephone?  

Cheers