How to remove header.Content-type?

[vicentelee]

So my proxy endpoint asks for a json payload. And the user will call the proxy by supplying a json payload and of course Content-Type to application/json.

However the target endpoint asks for a application/x-www-form-urlencoded. I've tried <Remove> and <Set> but not matter what I do, I can't seem to get rid of header.Content-Type.

I've tried removing this header.Content-Type in AssignMessage as well as a ServiceCallout.