Each service would be an Invoice. You can create month end Statements. Statements are designed to pull info from unpaid Invoices. You can email either or both to your customers. If you sign up for payments you can even give the customers the ability to pay the invoice directly from the email by credit or ach.
You cannot create just a Statement without an Invoice. When you receive payments you post against Invoices, not Statements. So if you bill monthly a single monthly Invoice is sufficient. Send Statements if you do not get paid per your terms as a reminder