I too have changed my job, but because my medicals have already been done and paid the RPRF fee too, hence my lawyer advised me that there is no need to Inform embassy about the job change as the embassy would consider my job details till the date I submitted my application...
You have to send them a case specific enquiry using the VOs website. I think there is an option to send attachments, just like email and you can send all necessary docs too.