Separate the relationship from the process
The account manager owns the relationship; someone else, or a system, owns the reminders. When the salesperson has to ask for money, both conversations suffer. When reminders arrive automatically and the account manager can say “our finance team handles that, but let me help”, the customer sees a process rather than a personal complaint.
Our view: a small business should never leave collections to the person who wins the work. Even in a five-person firm, give the job to the owner or the bookkeeper, with the salesperson informed.