In order for you to federate with Skype for Business and Consumer Skype users, your Skype for business online (O365) will need to be disabled.
Please follow the steps below:
1a) firstly you will need to Remove the license from each "Active User" from the Office 365 portal (https://portal.office.com):
b) Select a user and then click "edit" within "Product licences" on the right of the screen.
c) Untick "Skype for Business" from the licenses:
Note: You must perform this step for EVERY user enabled in Office 365.
2a) You will now need to Remove External Communications for Skype for Business Online to consumer Skype users
b) Expand "Admin centers" and then click "Teams"
c) Click on "Legacy Portal"
d) Select "Organization", then "External Communications".
e) Untick the option "Let people use Skype for Business to communicate with Skype users outside your organization" and click on "Save".