Deleting duplicate information

Hi Dears,
with following codes i send some information to DataBase via Submitcust.php . but i want to prevent from data duplication in some items like phone,Email,.... beafore data sending to DataBase.
so i added some codes for checking but it didn't work. please help me for that.

I have removed the link you put in as a tag, as this opened the contents of your tinywebdb php database !!

Thanks a lot