First of all, the employees are afraid. They feel that they might not do a very good job selling, which is perfectly reasonable; they don't have the training and experience that the sales staff has. So why should they even try? Then they might not find it to be profitable. This is harder to fix, but all in all, they don't see sales adding on to their own salary.
How can you fix this? Well you need to motivate your people. The best thing you can do is call everyone in for a meeting, even those in sales employment and explain that there are going to be training sessions. These sessions will teach the non-sales staff the art of selling, and when they have the knowledge that they need, they will no longer be nervous or afraid about selling the product.
The employees in sales jobs can also contribute to this effort. Though they might not be administering the training sessions themselves, they can use their background in sales employment to help the other employees learn the ropes. They can even serve as mentors, answering any questions that might come up, and even taking over situations that become too complex for those who aren't actually in sales jobs. But even when you get this down, there is still that other issues to take care of. The issue is of employees who don't see how this can help their salary.
You probably don't have any room in the budget to award commission to every standard employee who makes a sale. Those in sales employment will obviously be making more money than the regular employees, simply because of the amount of money they bring into the company. It also requires special training to actually be part of jobs in sales, and that is because of the confidence and negotiating skills required.
The best thing that you can do to resolve this issue, is offer rewards to regular employees who sells the most in a month. For instance, if you run a retail store, you could have impulse item competitions with the cashiers. The person who sells the most impulse items wishes some type of award, whether it's cash, or merchandise. This will motivate your people to start selling, and is something that should be introduced in any company. This is just one of the many ways that you can motivate your employees.
Jobs in sales become more complicated when you need everyone to sell, but when you do get everyone to make sales; it becomes easier, and definitely more profitable. So give it a try and see how it benefits your company. More than likely you'll be more profitable before you know it.