A group of Amazon.com Inc. employees who pushed the company to combat climate change say Amazon has threatened to fire some of them if they continue to speak out about their employer’s internal affairs...  Maren Costa, a user experience designer, was threatened with termination after speaking to the Washington Post... “This is not the time to shoot the messengers,” Costa said in the release. “This is not the time to silence those who are speaking out.”... Jaci Anderson, an Amazon spokesperson, said... Employees are “encouraged to work within their teams,” and may suggest “improvements to how we operate through those internal channels.”...[E]mployees say Amazon changed its policy on workers speaking to the media after workers had announced the September walkout. The updated policy requires employees to seek approval before speaking about Amazon in any public forum in which they’re identified as an Amazon employee... “I encourage you to review the policy again and in the future anytime you may consider speaking about Amazon’s business in a public forum,” Eric Sjoding, an employee in Amazon’s human resources group...