A method of authenticating a service agent on behalf of a user, the method performed at a server and including: obtaining a unique identifier associated with a first communication session established over a first communication channel; storing the unique identifier in a data store; receiving, via a second communication channel, a validation request comprising verification information associated with the user; attempting authentication of the service agent by comparing the verification information with the unique identifier, and in response outputting a validation response via the second communication channel. If the verification information corresponds with the unique identifier, the validation response indicates successful authentication of the service agent, and if the verification information does not correspond with the at least one unique identifier, the validation response indicates unsuccessful authentication of the service agent.