The first step in assessing the controls within a newly implemented call center is to evaluate the operational risk associated with the call center. This will help the IS auditor to identify the potential threats, vulnerabilities, and impacts that could affect the call center's objectives, performance, and availability. The evaluation of operational risk will also provide a basis for determining the scope, objectives, and approach of the audit. The other options are possible audit procedures, but they are not the first step in the audit process. References: ISACA Frameworks: Blueprints for Success, CISA Review Manual (DigitalVersion)

A digital signature is a mathematical algorithm that validates the authenticity and integrity of a message or document by generating a unique hash of the message or document and encrypting it using the sender's private key1. The primary reason for using a digital signature is to authenticate the sender of a message, as only the sender has access to their private key and can produce a valid signature2. A digital signature also verifies the integrity of the data, as any modification to the message or document will result in a different hash value and invalidate the signature1. However, a digital signature does not provide availability or confidentiality to the transmission, as it does not prevent denial-of-service attacks or encrypt the entire message or document3.
References
1: Understanding Digital Signatures | CISA
2: Signature Verification | CISA
3: SECFND: Digital Signatures from Skillsoft | NICCS