Just been through something similar – they couldn't get a line working nor port my old phone number over.
Expect several expensive mobile calls to their 0845 number followed by broken promises of someone calling you back.
In the unlikely event of someone calling or responding to email, expect to be given a false promise of when your line will be working. And despite what they say, there isn't anybody "personally looking into it".
Repeat several times over.
In the meantime, you'll be charged for the services they're not supplying even if they've promised you they won't. Cancelling the direct debit is a great way of ensuring they finally get in touch with you.
You'll then get a succession of head-scratchers turning up at your house, but leaving without actually doing anything.
Good luck! 😀