How does Caller ID spoofing work?

Question

Telephony

As far as I know, mobile operators prohibit calls with the substitution of the Caller ID field. But, services such as spoofcard.com allow you to substitute. I also found many VoIP operators that allow you to put a random number in the Caller ID, but this number needs to be confirmed. It turns out that they limit the substitution of Caller ID only programmatically, but they have the ability to set any number.
How can this be?

Answer 1

Long distance and international operators can skip any CID.
VoIP operators are usually attached to some kind of foreign operator or to a Russian one with an international license.
On Rostelecom networks in many places, any mortal connected via E1 can substitute any CID, but these are more exceptions due to the curvature of the settings or restrictions on the side of the operator's iron.