People are embarrassed when they haven’t paid their bill and other people know that. Rather than you call your customers a third party like your accountant might be able to get on the phone and call your debtors for you.
There are many people that could call on your behalf. You accountant, a Director, spouse, business coach or a credit agency.
If they can log into your accounting system and review receivables they can easily ring and enquire as to why a payment hasn’t been made. Load phone numbers for your customers so your accountant can quickly identify the people they need to call and their number.