Is it with the call centre or customer service centre? If it's with the call centre, then it'll be something along this lines:
The phone interview takes about 15 minutes. They'll ask you 3 or 4 questions. Once you get started it's not too daunting.
The next step is a group assessment which takes between 3 and 4 hours. There, they assess how you work as a team member and as an individual. You'll be required to do a phone role play for about 5 minutes, 5 minute typing test, and a small group activity.
The 3rd stage is an interview with the managers which can take anywhere between 15 and an hour.
Once you've passed those 3 stages, you'll be required to have a medical and eye examination.

Good luck and keep us updated with your progress.