Please follow below instruction to Edit your Mobile Numbers .
To update your mobile number follow below steps:
1. Sign in to Outlook Web App (https://portal.office.com ).
2. Click on Mail Icon
3. Click the gear icon ( Settings) to open to open the Settings menu, and then click Options.
4. On your option page, click the General button and then My Account to update mobile number and Save it.
Please Click SEND/RECEIVE and click on Download Address Book… to sync latest Global Address List, it will help you to see the latest information from server instead cache.
Feel free to let IT Ops know in case need any help. Thank you!!
Thanks
IT Networks & Support