proposal
A jingler
You could tell the person on the phone that your going to put them on hold for a minute, then answer the other call and ask them to call back later, then continue your conversation with the first caller.
you call the first person you wanted to call and then press flash and then called the second person and then press another flash and there you go , a three way call.
To the point
A secretary writes letters for a manager.
guider
A secretary
A person who constantly writes letters of complaint can be referred to as a chronic complainer or a serial complainer.
biographer
The person who makes a will (or 'testament') is a testator.
A Philosopher
A person who writes the libretto for an opera is simply referred to as the librettist.
A drawer.
proposal
A poetry
publisher