This can occur is if multiple individuals are associated with the same calling number. (Travel agencies, businesses etc).
To determine if this is the issue you are experiencing:
- Navigate to Tracking > Inbound Calls
- Enter the calling number from your lead form into the phone number field for the lead
- Click Get Data
- Review the Inbound Call Tracking report to determine if there are large number of calls coming from that phone number. You can even go a step further and listen to call recordings to determine if the calls are coming from different people. If this is the case, you need to configure a no-data-dip for that phone number.
To do this please see the article titled: No Data Dip Numbers