Short for Quality Assurance. This is usually a group within a business that monitors the quality of work that it's employees are doing. More specifically with phone customer service work, they grade a certain amount of calls each month to make sure that certain guidelines and quality standards are being met.
That must've been a perfect call because QA gave me a 100%!
When business is slow enough that your employer lets you end your day earlier than your scheduled shift. Some employers will also offer green time as coming in later than our scheduled time when business is slow for night/2nd shift shift workers. These can be offered on a paid or unpaid basis.
The phones were dead today so my supervisor gave me some green time.