How to get an old phone number onto a 3G iPhone?

Sorry for the badly worded question but I don't really understand?!

Basically I've been given a 3G iPhone 4S and I want to put the sim card from my iphone 3 because I want the number to be the same (they're both pay as you go, btw). But I just realised the 4S card is much smaller than the older one so it obviously doesn't fit. Is there any way to keep the number or do I have to buy a new sim?

Contact your carrier

You need a new nano (micro) sim, then ask to get your current number "ported" to your new SIM card. The SIM should be under $10 and the porting should be free.

  • Switching number from Verizon to Straighttalk AT&T. How to keep my old number? Right now, I have a Verizon noncontract phone. I'm buying an iPhone 4 from a friend which is on the Straighttalk AT&T micro sim plan. I'm moving to the Straighttalk AT&T plan and need to know how to get my number changed over and where to get a new micro SIM card from.
  • Need to get a number from my phone without having my phone. Possible? I left my phone at a friends house but they are not home so I can't just go get it. Is there a way to use find my iphone to get their contact out of it so I can call them from another phone and tell them its t their house?
  • Just switched my number to a new iphone, but my old phone still works? I just went and started an individual plan and got a new iphone 5, and they carried over my number from the virgin mobile prepaid i had before. My new iphone can make calls and send and receive texts… But so can my old phone. And when i called my cell number using my house phone, my old phone rang, but my new iphone didn't. Do i have to like cancel service or something? I'm confused about what to do, the guys at apple didn't mention anything about it.
  • If I call someone while signed onto Skype, will my phone number show up on their end? As opposed to physically dialing a phone number, I used my iPhone to call someone on Skype after signing on to Skype with my e-mail and password. Therefore, I simply clicked the "phone' icon. Since I was using Skype from my iPhone, will my mobile number show up in that person's missed calls?