When a telephone is answered on behalf of another person,
a clear and concise telephone message or telephone memo should be written.
In a telephone message, there is necessarily a heading and the subject part,
and sometimes there are boxes to tick showing what to do about the call,
i.e. call back, wait for call, etc.
The Heading part includes: 1 the time one gets the telephone;
2 the person to whom the message is intended;
3 the caller’s name; 4 the company, office, or work unit the caller is in
(This is especially important in business occasion);
5 the caller’s telephone number or ways to contact;
6 the name of the person who gets the call or who writes the memo.
Most organizations or companies have a memo/message pad specifically designed.
They list the most frequent occasions with box for the message taker to tick,
whether it is urgent or it demands a return call.
Sometimes it is important to write down a specific direction or message. 
This must express clearly and briefly what the caller wishes to communicate. 
Keep a pen and note pad by the telephone.
To get the message accurately
(such as the caller’s name, title, the company, telephone number),
the message should be repeated to the caller to confirm.