How to unlock a phone blocked by the operator?

When you say "operator", I am taking this to mean the "carrier" or "provider" of the cellular service.....correct?

The carrier locks the phone

Only the carrier can remove the lock on the phone

If you purchased a phone from another person and it is carrier locked, you will need to return the phone to the seller so they can have the carrier remove the lock. The carrier will not do this unless they are talking to the customer that established the cellular service.

The carrier will not talk to you.....because you were not the person who established service with the carrier.

If you cannot locate the person who sold you the phone, the carrier will not unlock the phone for you....because you were not the person that established service with the carrier. In a case like this, you have a useless phone that will never work correctly.

Return the phone to the seller for a refund.

You may be referring to 1 of two things:

• Activation Lock - This will say it is locked to the owner when you attempt to open it. You cannot remove the Activation Lock on a device without the original owner removing it themselves. It will remain unusable.
• Carrier Lock - This is a lock provided by a cell provider so you cannot use it on another service. Only the carrier that locked the device can remove the lock. If you are not a customer of that cell provider, they are unlikely to unlock the device.

My recommendation would be to return the device and get your money back. If the seller is no longer available, then it is possible you were scammed. Review the article here about the problems you can experience when purchasing a device from an unknown seller.

The All Too Common SAD Reality of Buying … - Apple Community

If you mean activation lock, you'll need to have the person whose credentials display unlock the device.