Hi Jeroen,
You can use instructions below to submit request to increase your limits, which is prerequisite for adding additional from addresses. Below method works even with Basic or Developer level support.
Please carefully follow instructions below to create a new Service and subscription limits (quotas) request to increase quota for Azure Communication Services.
1. Navigate to this link to start the process:
https://portal.azure.com/#view/Microsoft_Azure_Support/HelpAndSupportBlade/~/overview
2. Click Create a support requestbutton at top
3. If you see Support AI Assistant as shown below, click Switch to old experience button on right. If not, proceed to step #4
4. Enter quota in the box and click Go
5. Select Others / Service and subscription limits (quotas) and click Next
6. Click Create a support requestbutton, as shown
7. Select Issue type: Service and subscription limits (quotas), Subscription: <subscription that needs quota increase>, Quota type: Other Requests, click Next
8. Open Notepad (or other text editor). Navigate to Email quota increase article, click Copy button in upper right to copy text, and Paste it into Notepad. Add your company info to the file and answer all questions, then save to a .txt file on your computer.
9. On Additional details tab. Enter description for your request, click folder icon next to File upload box, and select .txt file you created in step#8.
10. Finish filling out Additional details tab, click Next, review and click Create. You should receive an automated email within a few minutes.
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP