No access to CP CoreApi

We have Email Address Sharing enabled in our side and thus we need to be able to modify the Logic by which Oracle selects a Contact when a not logged in user starts a chat.

When going through the /core/ code I found that in the Chat Model the authenticateChat() function takes care of sending the data to the ChatServer and creating the JWT. I created my own copy of this Model so I can modify the logic, however I have the following problem:

There is a CoreApi function used: $apiResult = CoreApi::chat_contact_auth_generate($chatType);
This function returns a session and JWT. Unfortunately it seems that I am not authorized to call this function from the Custom Models folder, as I get the following error: