How Do I remove the SIM card from the iphone?

I'm trying to switch back my old phone and stop using my iphone, I dont want to pay for things on the iphone i dont use anymore. And i was told be someone via email from AT&T to remove my sim card from the iphone and I was wondering if anyone knew how to do it?
ok I just found out how to get it out due to youtube, but i have a new question, if you take out the sim card and put it back in will it work normally, like if you were to take the sim card out of any other phone…?