The underlying infrastructure for telecommunication allows the Caller ID number to be any phone number. For most consumer-grade phones, the provider does give the user the ability to change this number. However, for commercial grade phone system, this feature is used to display a common phone number on all outgoing calls, such as in a call center.
Attackers use this ability to modify the caller ID to trick the end user to either taking a call or attempting to add validity to the call.
If the caller is requesting non-public information or for you to perform a high-risk transaction, do not provide information or perform the action until the request is verified as authentic and authorized.