I have a bunch of app services listed in API management. These services call third party clients who want to whitelist my IP

I would like to give them the public IP address of the APIM instance. I tried to check this by having my app service hosted in APIM call a dummy function app I had created. In the dummy function app I logged the header details.

It appeared that the IP coming through was that of the app service and not the APIM instance. I was expecting (and hoping) it to be the APIM IP