If the stored procedure provides the only data in the report, there are two options that I can think of:
1. In the report, go to the database menu and turn on Select Distinct Data.
2. Modify the stored procedure to return distinct records.
However, if the stored procedure already returns disctinct records and is just one of several data sources for the report, you're probably seeing the duplicate records because of the one-to-many relationships with one or more of the other tables in the report that make the actual SQL not return distinct records. In this case, the best way to handle the situation is to group on a field or combination of fields that identify a distinct record. Put the data that's now in your details in either Group Header or Group Footer sections. If you're using any summaries (sum, count, etc.) you'll also have to rework them because they'll be inflated due to the multiple records.
-Dell