Hello, Syam_, You will not be able to connect your Cisco IP phones directly to Skype for Business Online. You will need a qualified endpoint, which you can find at the link below: Getting phones for Skype for Business Online https://docs.microsoft.com/en-us/skypeforbusiness/what-is-phone-system-in-office-365/getting-phones-for-skype-for-business-online/getting-phones-for-skype-for-business-online
Nick
Senior Infrastructure Architect (Lync)
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