I worked as a customer retentions advisor for Virgin Media through an outsourced agency called Sitel. It was our job to persuade the public to stay with Virgin Media by offering exclusive discounts. It was a commission-based job, and the commission was uncapped. After six months as a team member - after working countless hours and fuck knows how much overtime, and after dealing with so much shit from both the public and the management - I was promoted to team leader. Great, I thought, the pay as a member was good, the pay as a leader should be better. Right?
Wrong. The commission wasn't just capped when I was promoted, it was stopped altogether. I was now on a fixed monthly wage, whereas before I was earning my basic wage plus commission. If was easily over £1500. As a team leader, I was lucky to take home £1000. Naturally, I was pissed off. I complained and said I wish to resign as team leader. They refused, and said if I wish to resign, I resign entirely. Obviously this was NOT an option. So cue more endless hours of slaving away for 'The Man' as well as dealing with the public, upper management, and now my own dimwitted team of phone monkeys.
After a further six months, after finding and securing a new job, I left Sitel/Virgin Media, and went to work for this new company - a call centre for a debt collection agency - as a team leader with an uncapped commission. The job was so much better than Virgin, but, yeah, it was still fairly soul-crushing having to deal with the public in such a manner. I saved up for a year, applied for help to go self-employed, and now I run my own business from home as a graphic designer. So much better than call-centre work.
TL;DR Don't do call-centre work.