No disrespect, but importing contacts to SIM Card is a bit old school. You can simply Sync all your contacts directly to iCloud - that way, you'll have access to your contacts no matter where you go or what device you use.
But, if you do plan on switching from an iPhone to different device, lets say Samsung Galaxy, in that case, I believe you can get all your contacts transferred to the new device at the Store (from where you bought the device) itself.
Hope this answers your question.