You can do it via logging into My Rogers - Overview - Sim Change. You will need to type in your current sim card number on one slot and the new sim card number on the other slot as it will instruct you to do.
You can do that or try Rogers Live Chat. They most likely will be able to help you.
You need to go into a Rogers authorized store or Rogers store and get a sim card. Most of the times they give them out for free. Ask them to activate the new sim card in ur account and add that sim card into ur phone.
Depending on what phone u get. If u get a other iPhone just back up the iPhone on iTunes and then restore the new one with the back up via iTunes. Samsung and blackberry have a app for this as well.