Microsoft has recently introduced the ability for Teams phone system auto-attendants to have the ability to transfer unanswered calls to an Office 365 Group. This is an excellent feature and will drop voicemails into your indicated Office 365 group visible in Outlook (desktop application, mobile, & web). 
But what if you want those voicemails visible in the same Teams:Calls:Voicemail as personal voicemails? 
To accomplish this, you will need a phone system licensed user account dedicated for this task (currently about $25 per month: Microsoft 365 Business Basic & Microsoft 365 Business Phone)
1.Create a new user account; let’s call them: MainLineVM
a. License appropriately with Microsoft 365 Business Basic & Microsoft 365 Business Phone
2. Log into Teams as new user and update call settings
a. Forward my calls to Voicemail
3. Configure Voicemail with greeting
4. Create a new distribution list; let’s call it MainLineDL
a. Make sure to allow outside emails to be sent to list
5. Add your desired users to said list
a. Please note that this will only work for internal users as the voicemail messages do not have a properly formatted “From” address and external email servers will most likely block it
6. Update your new user account (MainLineVM) to forward to your newly created distribution list (MainLineDL)
a. We recommend making this update via the Microsoft 365 Admin Center
7. Update your call flow to redirect to “Person in organization” -> Select your new user account (MainLineVM)
a. Please note that this process will also work with a Call Queues
You should be all set now to have incoming voicemails be directed to user’s Teams:Calls:Voicemail. You could get creative with Outlook rules to direct incoming voicemails if you wanted to re-use this account for multiple AAs/CQs but please use at your own risk. Reach out to us if you have any questions or if you would like help deploying your phone system through Teams.