Zoho Form to Desk integration keeps creating new contacts.

Zoho Form to Desk integration keeps creating new contacts.

Hi,

We have created a form via zoho forms that our clients use to request new users to be added to our software. The form then submits a ticket on their behalf on desk via the integration, however I have noticed that when doing so, it keeps creating the submitter as a new contact even if their details already exist. Is there a way to get this to stop? I have tried using the first and last name contact fields, and the email address but it still happens.

Kind regards,
Ollie