IP Address in Enpoint Manager

I’ve looked around and can’t seem to find the answer for this. I have a system with 2 nics, one with an external IP and one internal. Endpoint Manager is giving my snom phones the external IP address for them to register to, instead of the internal. How do I get it to change its mind? I tried putting the internal IP as both internal and external in the global settings in Endpoint Manager but that doesn’t seem to actually do anything.