The easiest way to handle this is to create two  different Job Templates which you can do in Advanced → Job Templates.

• The first template is for the various visits.
• The second is set to Invoice and Close the Job and would be for the monthly billing.

Note: This is recommended if the monthly rate is a flat amount.

Alternatively if you bill your customer per visit, you can use the Bulk Invoicing from the Job list which then converts multiple jobs into a single visit.