Unable to connect SharePoint designer 2013 External content type with Wcf

Hello Everyone,

i Am new to connecting Wcf service to SharePoint designer external content type.

SharePoint designer version : SharePoint designer designer 2013

SharePoint Version : SharePoint Online 

i have created a wcf service and when i try to create a external content type i am getting the following error 

 my web Config File

Can Someone Please help Me??

Thanks,

Syed