Well I guess after four attempts they should have got it right but obviously not
I do'nt know the criteria NTL have when they interview people for positons in customer service, but I would think that the ability to keep a level head to be an important one, anyone who can't keep a level head, ie not shout at customers should be demoted to opening the mail, or better for all concerned sacked.
The promised call back, yes this is used when the cs member has no idea what to do once all other avanues have closed, I have yet to know anyone, myself included, who has had a call back from this rat bag of a company.
Hopefully your issue will be sorted.