1. You don't have any credit.
I need to top up.
2. Your mum's phone is engaged.
I need to call back.
3. You want to communicate with your friends. They're outside, but you're in the library.
I send a text message.
4. The telephone conversation is finished.
I hang up.
5. You're bored with the ringtone on your phone.
I download a new ringtone.
6. You phone a number and it isn't correct.
I say “I'm sorry, I've got the wrong number!”