How do we ensure a call recipient's caller ID will display a particular user's phone number rather than the main company number?

We want to ensure that a call recipient's caller ID will display a particular user's phone number for an incoming call, rather than the main company number. So far we have not been able to see the correct user's number appear in a recipient's caller ID, just the main company number.

We followed the example given here:

var session = webPhone.userAgent.invite('PHONE_NUMBER', {
    media: {
        render: {
            remote: document.getElementById('remoteVideo'),
            local: document.getElementById('localVideo')
        }
    },
    fromNumber: 'PHONE_NUMBER', // Optional, Company Number will be used as default
    homeCountryId: '1' // Optional, the value of
});

.... from the ring central web-phone sdk - https://github.com/ringcentral/ringcentral-web-phone, but specifying the 'from' number doesnt help.

So insight into that would be much appreciated. Thank you