Question: In a 3GPP-compliant telecom network, what is a required functionality for a cost control mechanism when a user's accumulated charges approach their set limit per time interval?
Option 1: Automatic extension of the limit without user interaction, ensuring uninterrupted service.
Option 2: Notification to the user requesting confirmation to extend the limit or apply Home Environment barring.
Option 3: Immediate disconnection of all ongoing sessions without prior warning to the user.
Option 4: Mandatory downgrade to a lower tariff plan to reduce further charges.
Explanation: This option aligns with the emphasis on user involvement in managing their charges. Notifying the user and seeking confirmation for actions respects user preferences while preventing unexpected additional costs, reflecting a balanced approach to cost control and user experience.