Rest Rcvr adapter : Bad Request 400

Hello Experts,

I have proxy to REST scenario in PO 7.5, using postman by setting content-type to application/json , I am able to post data to service.

In the config scenario, in rcvr rest adapter I have specified the same URL , additionally Set HTTP Header "Content-Type" to "application/json" , but I get same error.

HTTP POST call to http://actualurl not successful. Bad Request

in the message monitor I can see the message in JSON , but content type is still text/plain and char set is utf-8.. is there any where else we need to add content type?

Also , What should be the value of Character Set name value in "Data Format" tab