Most customer service is defined by how a company treats "external customers" but there is "internal customer service" as well. What do you think?

In my opinion, internal customer service are much more important than the external ones.

If a company fails to well treat the internal customer service, they will rebel; their rebellious acts may be transferred to the way they treat the external customers leading to poor customer service, higher customer turnover, and causing the company to lose money.

Therefore it is better to concentrate more on the internal customers first so they would take care of your external ones.

Most certainly. If you can not treat your colleagues well, how will you be able to serve customers well. Like the good all saying goes "Charity begins at home".

Expanding your definition of customer service to include co-workers will lead toward even greater success.

The internal customer chain is just like the external. We are all customers both inside and outside the company or organization.

"Poorly Treated Employees Treat Customers Just as Poorly".

yes, I agree with this concept and I think the hardest work for who work in customer service it's coming after wrong deal or selling.