Support number unknown?

[#1]

I am attempting to ring customer support.  The number listed is 0330 1239 123 but as soon as I type the 9, I get a "number not recognised" message.

What gives?

[#2]

That sounds like an issue either with your handset or your phone carrier.

What phone handset are you using ?

Which phone service provider are you using ?

FWIW, I just tried dialling that number from my VoIP landline and immediately got the "Welcome to Plusnet" greeting.

[#3]

Is it from any phone instrument or mobile, or just one.
If it's the latter – just a shot in the dark – possibly a sticky "3" button, which can't cope with two successive presses.
Try leaving a second or two between presses.

[#4]

The issue was that my line had been cut!!  A warning to anyone else who is switching to fibre that OpenReach might cut yor line before the fibre is installed!!  In my case the engineer needed a hoist to attach to the pole and could not find one available.  Had to wait a week before someone came back and discovered the same problem 🙂  Finally found a hoist and fized it.