Landline not working

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Level 1b

NBN installed, internet working fine but despite following all instructions regarding setting up the landline.  It's not working.  Dial tone sounds okay, but when you dial a number you just get a continuous high pitched tone.  The light on the front of the modem does not light up a although the phone is plugged in to the phone plug.  I've tried both 1 and 2.

Thanks