Dear [First Name],
 
We are writing to request payment for the outstanding balance of [Amount Owed] on your account. Despite our previous attempts to contact you, we have not received payment for the past [Number of Months] months.
 
We understand that unforeseen circumstances can arise, and we are willing to work with you to find a resolution. However, we must receive payment or a payment plan from you within the next [Number of Days] days to avoid further collection efforts.
 
Please contact us as soon as possible to discuss payment options or to set up a payment plan. We want to work with you to resolve this matter to your satisfaction.
 
Please note that if we do not receive payment or a payment plan from you within the next [Number of Days] days, we may have to take further collection action, including reporting the debt to credit bureaus or initiating legal action.
 
We value your business and hope to resolve this matter as soon as possible.
 
Sincerely,
 
[Your Name]
[Your Company Name]