Students should try to provide as many different excuses as possible to explain why the person calling them cannot speak to the person s/he wants to. Example: "He is having dinner" or "She is walking her dog", or "They are flying to Madrid in 5 minutes". This activity can also be used for present and/ or future uses of Present Continuous.
The credit for this warmer idea goes to Alex Case at TEFL.net.
Have a warmer idea or a nice ice-breaker? Please share!