When the installer has finished routing cables and plugging the Cable Modem into them he will leave you with a whole load of account information and a CD.
Throw the CD in the bin!
Follow the instructions
HERE to set your account up.
You only need to phone NTL if you need to talk to them about anything, for example if you live alone and get lonely, or if there is a serious problem with your service. The actual activation of your BB account can usually be done online and any tech support type problems / questions that you get can normally be answered by somebody in here.