I handled inbound calls, those seem to be mostly customer service with some selling, at least mine was. Customer service over the phone is terrible, especially since most of the time they're upset and take their frustration out on you (sometimes they even apologize beforehand then tear you a new one). It was like earlier said, soul-sucking. I got all kinds of people; stupid angry people who won't reason, depressing situations that people were in because of an error in billing, normal people who understand how troubling it is to be in a call center, and people who were upset because they were transferred over and over on the phone, ect.
I always looked forward to the end of the day when I'd smoke a bowl or two and unwind after a stressful day. Wish I had some now :|