It is recommended that Skype for Business Online customers start with “Islands” mode so users can experience the full functionality of Teams at their speed. Then, once organization adoption of Microsoft Teams hits 100% saturation, businesses should upgrade to “Teams-Only” mode.
For more tips like this, check out the working remotely playlist at www.youtube.com/FoetronAcademy . Also, if you need any further assistance then you can raise a support ticket and get it addressed.