I have just upgraded to fibre broadband and want to divert all landline calls to a mobile. I tried 21xxxxxx# but did not work. Can someone advise me how I can complete this silly task?
are you on BT digital voice with bt handset? if so
https://www.bt.com/help/landline/all-about-call-diversion-for-digital-voice
free if you have BT mobile