guest mobile user skype for buisness

[h-i-k]

We use skype for business with an E3 account.  If we send an invitation to a guest user who is on a pc or mac, they are able to use the skype web app and sign on without a Microsoft account.  I have not found a way to the same for a mobile user.  The mobile user is forced to download the SFB app and sign in with a Microsoft account.  Often she is blocked from joining the meeting because the organization does not allow joining the meeting.  I have added the user to my AD (without an office license) and they are still blocked from joining the meeting.  Is there another way for a mobile user to join a meeting without a Microsoft account?

[#2]

For Skype for Business Guest users for joining the Skype for Business Meeting they need to join the meeting using Laptop/Desktop.
Users who are trying to join the Skype Meeting through Mobile Devices they need to have Skype for Business Application with the Login Id and password.

This is a default feature for Skype for Business Online and Skype for Business on premises.

Regards,
Satish

[#3]

I should have updated this a while ago but after assistance from the Microsoft help desk, there is a way for mobile users to join skype without the login.  They have to download the app.  When they answer the invitation the app asks for username and login and there is an option which states I don't want to sign in.  Then it will allow you to join the meeting without having a user account.