It's too broad a statement to say that absolutely everybody is your customer. But, you actually never know if the next person you speak to could be a potential customer so you should treat them that way. Treat them the way you would want to be treated no matter the roles you are currently in. Let me explain.
The Thank You Economy
I'm recently back from a holiday and during that time I picked up the Thank You Ecomony by Gary Vaynerchuk again - I'd read a number of chapters but never got around to completing it. The Thank You Economy website provides an overview of the idea:
The world of business is coming full circle. The rise of the Internet and the empowerment of the common consumer has created a fundamental shift in how businesses are expected to behave.
To take advantage of this opportunity, businesses will need to look backwards and scale the caring their grandparents' businesses exhibited towards their customers or watch their competition pass them by.
Fundamentally it means give a crap about your customers and build relationships with them. A real relationship will result in real loyalty and thanks to social networks the word will spread about you and your business. There's also an emphasis about ensuring you focus on long-term rather than short-term wins as customers will see through this. The relationships have to be genuine to really work.
The Thank You Economy focus is customer service and this is something I feel very strongly about.
When I'm trying to help somebody I really do care about the service I provide - sometimes to my own detriment. So, if they're not happy with the service I've provided it affects me. The problem is that sometimes you just can't win. It might be that somebody is just looking for conflict. It might be that the situation is at a point where you can't be your normal friendly way, nothing you can do is good enough and you just need to tread carefully and not take things personally.
In these difficult situations you are in the role of the B2B customer service representative and you are providing a service to a customer. But what if that customer also has a B2B service, or one day works for one? There's a chance that your roles may reverse and they might be trying to sell you a service or even providing you customer service. Even if that's not they case they still represent the company that they own or work for. The way they are acting reflects on their company.
Treat everybody as a potential customer
The point really is to treat everybody with respect and the way that you would like to be treated. It might be that in one particular conversation you are the customer and they are the customer services representative. You, as the customer, might feel that you've been unfairly treated and you might want to take it out on somebody.
They work for a business and although in the present conversation you are the customer and they are the service provider you should still think of them as a customer. If you handle the situation correctly, and treat them as you would like to be treated, they may well be a customer some day. If you are difficult and unfair then it may mean that they will be highly unlikely to use any service that you are part of.