Hi Modestas,
You can switch your subscription using the offer option. I recommend checking this article for guidance: https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/switch-azure-offer.
Additionally, you can reach out to the Microsoft billing support team for assistance:
If this is helpful please accept as answer or upvote.
Best regards,
Dillon Silzer, Director | Cloudaen.com | Cloudaen Computing Solutions