Hi David,
You can create free Quota request and then on Additional details tab explain that you need Alphanumeric Sender ID capability enabled for your ACS. Normally you would create Technical support request for this, however, that requires minimum Standard support plan.
Please follow my instructions below to avoid getting stuck in endless loop:
1. Navigate to this link to start the process:
https://portal.azure.com/#create/Microsoft.Support
2. Enter quota in the box and click Go
3. Select Others / Service and subscription limits (quotas) and click Next
4. Click Create a support request button, as shown
5. Select Issue type: Service and subscription limits (quotas), Quota type: Other Requests, click Next
6. On Additional details tab, Enter description for your request
7. 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