"all circuits are busy now"

forgive me blowing off steam but this problem is driving me bonkers. I’m in the UK and I can dial normal (11 digit) numbers from my usual extension no problem but I’m trying to get it to work with the NHS 111 number. In the freepbx outbound routes I have a dial pattern 111 entered, I did submit and ‘apply config’ but it didn’t work. Also in the trunk page I have 111 entered under ‘Dialed Number Manipulation Rules’ but still it doesn’t work. All I ever get is ‘all circuits are busy now’. Can anybody help please?