Jest partial mocking from the same file

I am getting crazy on mocking with Jest. I feel that I have a fairly simple case that I cannot get to work.

I have a service extensions.service with a bunch of functions:

async function getSplitCost() {
  // Check if feature is enabled for the customer
  const isEnabled = await isExtensionFeatureEnabled().catch(err => {
    throw new Error(err);
  });

  return {
    split_cost: [],
    feature_enabled: isEnabled
  }
}

async function isExtensionFeatureEnabled(): Promise<boolean> {
  console.log('Function is executed');
  let serviceStatus = await servicesService.getServiceStatus('service1').catch( err => {
    throw new Error(err.message);
  });
  
  return serviceStatus;
}

export default {
  getSplitCost,
  isExtensionFeatureEnabled,
};

I now want to create a test case that should validate the function getSpitCost and mock the response from isExtensionFeatureEnabled without running the function. Example that I have tried below:

jest.mock('../services/extensions.service', () => ({
  __esModule: true,
  ...jest.requireActual('../services/extensions.service'),
  isExtensionFeatureEnabled: jest.fn().mockResolvedValue(false),
}));
import extensionsService from "../services/extensions.service";


describe("getSpitCost", () => {
  it("should return empty split cost when extension feature is disabled", async () => {
    const result = await extensionsService.getSplitCost();

    expect(result).toEqual({
      split_cost: [],
      feature_enabled: false
    });
  });
});

As I am not calling the function isExtensionFeatureEnabled directly I cannot use spyOn. However, even though I mock the response to false the actual function is being executed. The extension service contains a lot of more functions that are being tested in the same test file, so I cannot mock everything. Also, I cannot split up the two functions to separate files.

How should I handle this?