Prompt When Duplicate Entry is made in Leads!!??

Prompt When Duplicate Entry is made in Leads!!??

I have a standard package with Zoho CRM. When i put a lead with an entry ( For Eg.Phone Number) which is same as the one in a nother already posted lead, ZOHO does not prompt me. 

Me and my team are unable to figure out duplicate leads while posting a lead. Is there any solution to this?