NTL have been bought out at sometime in the (recent?) past by another media company, UPC.
It seems that as part of this exercise, they have implemented a new billing system and have had significant customer service issues as a result.
See here:
http://www.boards.ie/vbulletin/showthread.php?t=2055018616
They also featured on Joe Duffy on Monday. Listen here, from about 15 minutes into the show (Real player required):
http://www.rte.ie/rams/radio/latest/Mon/rte-liveline.smil
My experience with NTL is that when it worked well, it worked well, and I had been a customer since they took over Cablelink.
However, I moved house recently and had no luck in getting NTL to set me up at the new address. I eventually emailed their customer service and sales email addresses with a deadline, which I doubt anyone ever read. Going to go with Sky instead, for one year anyway (they had a promotion recently).
In light of the situation that seems to exist within that company at the moment, I would be very slow to sign any direct debit mandate.
Hope that helps,
Paul.