First, let me share my simple-minded distinction between a related pair, sales and marketing. Sales lets you buy something you already want, while marketing makes you want something you didn't use to want (so that you'll go on to buy it). It makes sense that they go together. A door-to-door salesperson typically has to do both. But in a larger corporation they are generally separate groups of people.
But sales and service? In my experience any corporation that combines these does a disservice to the customer. And the more closely they are combined, the worse the service.
When you buy something, chances are it won't work so well after a time. Then you get it serviced. Car dealerships are one example. But if you go to the same place you bought your last car to get it serviced, chances are you'll walk through the showroom and, what the heck, just buy a new one. At least that seems to be the corporate strategy.
At least a car dealership doesn't have the very same person doing both the service and the sales.
For example, consider a local phone company, Quirkiest*, where when you call to get service, they seem to feel they have to sell you something else. The problem is that it's the same person--the one who is supposed to be serving you--who is rewarded for how well they sell you something else.
A couple years ago we called to prepare for a move. Then, when the move was delayed, we called to cancel. The "service" we got, as we found out a couple months later, was that we had been "sold" an expensive internet package (huh? that never even came up). So, when we finally did make the move, there were two bills waiting for service that we never even got because we weren't there yet. We got them to reverse most of it, but not without a fight. Come on! We wanted service, we called the service number, but we got sales.
We no longer do business with that company, but get our phone service from Skype. Great service and low-pressure sales (it's there if you want it).
Or what about Clawfoot* Door Sales? Actually, the name says it all, really. It turns out that all they really do is sell the doors. When the doors don't work, and you communicate that you really did expect them to work, they send out someone who isn't competent to make them work (and doesn't) and charge you anyway for the service call.
The best bet will be to get (and pay for) another company to come in and actually make them work. Which is my point, really, that sales and service ought to be kept separate. Caveat emptor --you've been warned.
*names changed to protect an innocent.