Problems when transforming GET request in api to POST in service

I have a Kong instance (dns * configured with a service with a URL

My service receives via GET and transforms the data to POST in the URL of my service. Everything is working, however, the POST received on my webservers that responds to the URL of the service arrives without the HOST in my http server log. It is like during the change from GET to POST the Host header was not sent.

Does anyone have any suggestions?