@Yevhenii Zakharenko Thanks for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.
Based on the shared information, I understand that your subscription is Azure Sponsorship offer and when you are trying to purchase a phone number it is showing that your subscription is not eligible to purchase the phone number.
To purchase phone numbers in Azure Communication Services, you need to have a subscription that supports phone number capabilities. Currently, phone number capabilities are available in the following subscription offers:
- Modern Customer Agreement (Field and Customer Led)
- Modern Partner Agreement (CSP)
- Enterprise Agreement*
- Pay-As-You-Go
Subscription eligibility offers changes based on the country in which you are trying to purchase the phone number.
** Applications from all other subscription types are reviewed and approved on a case-by-case basis. Reach out to acstns@microsoft.com for assistance with your application.
Feel Free to reach back to me if you have any further questions on this.