I work as Technical Support Engineer and I deal with clients all across the globe.
The most challenging part is even when I am the only person trying to help my client, sometimes they dont understand this. For them I am a representative my whole firm so everything that went wrong whether due to their own or someone else's mistake , eventually adds to their frustration by the time they reach me .
Despite trying to help them I also have to listen to all their complaints and sometimes harsh words. So the most challenging part is to still keep my focus and work on getting their issue resolved. I keep thinking how happy the customer would be by the end of it and that drives me to help overcome the challenge.