The scope of your question is pretty broad. A lot depends on how your database is already configured, your desired final result, and your development abilities.
What have you already tried? Can you post a more specific question? Have you considered hiring a FM developer to do this work?
I'll second David Jondreau's comments.
Here's a thought. I assume that you allow the salesperson to make notes of each sales call. I'll also assume this is in another table. Let's name the table for the person getting called as Person and the Second table SalesNotes. These would be related, so a salesperson could click on a Person and see a list of SalesNotes. A typical implementation might be to have a layout for a Person and add a portal for related SalesNotes.
For your specific purpose you could create a list layout from the context of the SalesNotes table and filter it for the last 30 days. FMP has a function for counting the number of items in the list, which will give you the number of total sales contacts for all salespeople. This list could also be filtered for each salesperson to give the number for each salesperson.
Here is an image of our current contact template.
Our sales person wants a total number of how many contacts she is making per week/month/year. Perhaps its a box labeled "contact" and our sales person adds a one each time she contacts (ie changes a 4 to a 5...then a 5 to a 6) , with a separate report that totals the number of contacts, and breaks it down by month? Completely open to other ideas and solutions.
We are open to outsourcing someone for an inexpensive, simple solution. Any thoughts?