I have had experience in research (landmine Monitor - ICBL) writting the research both in spanish and english during 3 years.
My previous experience has been providing customer services in english (not native language) in different call centers in Panama. One of them was an interpreter call center (Language Line).
The work in call centers has been in different capacities: agent, mentor, supervisor and work force coodinator. Also, I was a facilitator for a Leadership Academy in one call center.
All of this work needed to be done in english, as all of the projects I've worked for have been for US based companies.
I'm not certified, however I know that the quality of production I can deliver is of high standars.