@Ruslan Shakirov
Since the Tenant and Subscriptions are on different regions, hence you have the limitation of not being able to associate them. Unfortunately, once the region is selected it can not be changed.
So here, we would suggest that if you do not have any data in the tenant, to create a new B2C tenant in the European Region and then have the same associated to the Subscription.
However, you may want to get in touch with the Billing & Subscription Team with a support ticket to check if there may be a possibility from the back-end.
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