Can you not elaborate for our experts here? Are you talking about landline or mobile calls or what? Do you have conventional telephone with answering machine or Digital Voice phones etc?
Well you can certainly access previously unanswered phone calls left on a DECT cordless phone if you buy one of those or if you are with BT you can avail yourself of their 1571 answering service. If I get a phone call when I am out any one who want to leave a message can when prompted so to do and when you get home you can pick up that call and hear what they have to say and phone them back if that is what you want to do. Many unsolicited callers of course hang up if no one answers and the Answerphone cuts in and prompts them to leave a message. I guess BT' own 1571 service is similar in operation.
Age is no barrier as I'm 86 by the way, so am no whizz kid but I persist and learn hopefully and Google is always your friend as is this excellent BT Community Forum.