I would have to concur that the people at the RGD are incompetent at best. I have been trying to get my duplicate certificates for months now and have had no success. I did, however, find out that the RGD is under the direction of the Jamaican ministry of health. If you contact Ms. Grace Allen-Young at the ministry of health, and let her know that you have had no luck with the RGD, she may be able to help you.
Also, which email addresses have you tried to contact at the RGD? I found that most of the ones on the website are invalid or unanswered. I did manage to get Ms. Holness's email address, I can forward that to you if you would like to contact her directly. Nobody who answers the phone there was ever any help to me.