What is a lock-in period?

The answer

A lock-in period is a minimum time you agree to stay with a service, and leaving earlier may involve a charge or the loss of a benefit. Not all plans have one. Ask whether a lock-in applies, how long it runs and when it starts, what the early exit charge is and how it is calculated, whether it restarts when you change plans or move home, whether the plan renews automatically and how much notice you must give. Keep the written answers.