I recently used a client’s phone after a meeting in his office. After getting back to my own offices, I received a call from him. 

Client: You need to fix my phone line RIGHT NOW. I can’t receive any calls.

Me: Are you calling me from your mobile?

Client: No, from my normal phone.

Me: The one that’s not working?

Client: Yes! I’m trying to call it now with my mobile and all I get is an engaged tone! It’s not picking up the call!

Me: Oh dear God.