Question: What is the primary purpose of storing the "Accumulated call meter" (EFACM) in a Subscriber Identity Module (SIM)?
Option 1: To track the SIM's storage capacity usage over time.
Option 2: To record the number of times the SIM is inserted into different devices.
Option 3: To provide an indication to the user for advice on call costs or as a basis for calculating the monetary cost of calls.
Option 4: To monitor the signal strength of the cellular network in different locations.
Explanation: The correct answer, Option 3, reflects the actual purpose of EFACM as per the provided context. It highlights the role of EFACM in providing users with an indication of their call costs or serving as a basis for calculating these costs, aligning with the principles of Advice of Charge (AoC) supplementary services. This demonstrates a nuanced understanding of telecom concepts related to billing and user feedback mechanisms.