Should phone be on to receive calls?

Assuming this is a cell phone ur talking about... If you want to answer the phone at the time, YES. but people can leave messages or voicemails. theyre the same thing, but cell phones say either one, not both. You can take out your phone later and it will say how many people, if any, have called you. it will show theyre number and everything, so you can call them back. Hope this helps!