Has anyone bought plane tickets in the post office? I've just recently heard that it's possible to buy plane tickets at the post office.
I'm looking for a reliable travelling agency to buy tickets to China where I can pay in cash. I don't want to use my credit cards, so I don't want to buy tickets on the Internet.

I think you can pay cash for your ticket at any official Chinese airline office. However not all the low fares you see online will be available on their system, and of course each airline office can only sell tickets for their airline.

the post office sells train tickets. but not sure about plane tickets.
another option would be going to the airport and paying at the ticket counter of the airline you want to fly with. the express bus from xiaoximen is pretty quick.

Isn't it possible to buy plane tickets at a travel agency with cash?

It is, the point is finding a good agency and I've heard that many agencies in China are scam.

Try CAYA travel agency, listed on GoK.

They deliver tickets and take cash.

Travel agencies book flights and take a commission. If there's a flight that's 200$ cheaper the next day, don't expect the travel agent to tell you about it.

If you want to find the best rates, you should search online yourself, then contact the agent with the flight numbers to book it for you.

@Magnifico I am aware of all this. What I'm asking about is which agency in Kunming is reliable.

Geezer answered your question then.

Most are reliable.