The most important job: Getting invoices paid

Due to this recession, most of your customers are delaying their payments as much as they can.
Receiving payments later means your company has less money on hand to pay the bills of your suppliers.
The Day Sales Outstanding (DSO) is increasing for the company, thus less cash.

Aside from all other functions and jobs, the most import one is getting the invoices paid. That is essential for the continuity of any company.
A deal is only done when the money has been paid and the customer is happy and confident.

Collecting the money of the invoices

Thus who is collecting the open invoices?
The accountant or the salesman?

The accountant has little or no relation with the customer and has little insight in the relationship or the problems with the products delivered or services supplied.

On the other hand the salesman knows his customers and is aware of the entire story of the different deals from the beginning to the end. He also has indications about potential further purchases, which can make him weak as he is already aiming for the next commission or bonus.

Can the Salesman appear to be the nice guy in order to keep the relationship going?
Whereas the accountant is then the bad guy as he is collecting the money?

Or should the Salesman collect the money and use the conversation opportunity to engage in a sales conversation if that is still possible?

Who is handling the collecting of the open invoices in your company?