my recorded response is in json. how can i change post content type to json
As far as I know, there is no way to directly change the content type to json, you can try to use JavaScript to convert to json, for example, use JSON.JSON.parse(str) or JSON.stringify(a) to convert each other
One thing to ensure if you need to make sure this request type should be json, is in the Request headers (Advanced > Request headers tab), make sure there is a "Content-type" that has a value of "application/json" that will force the request to be sent as JSON type.