The sim in your i830 should be yellow as well. Any yellow sim will work in the BB 7100i. My advice, a Nextel rep for many, many years, do not put the white sim card into your 7100i. Dont get me wrong, you can put it in there to upload your information, but you dont want to be using that sim. The main reason being all warranties, insurance and service plans will be void, and problems may occur sooner or later. See if the person on ebay will provide you with the sim# if applicable, and the pin, and check those with Nextel to make sure the phone is ok.