Can i use my sim card from a samsung phone in the iphone 3gs?

I have been told that you can't use a sim card from another make in the iphone 3gs that it has to be cut to fit it is this right i have a samsung gts3650 and don't want to have to put all my details etc and have to have a new number if i buy my sister in laws iphone 3gs

I don't think so

You are going to have to get someone to cut the sim card for you because an iPhone card is smaller. Look on your local craigslist for people offering this service. Keep in mind that you may also have to unlock the phone depending on the situation. IPhone 3GS is a relatively old model and you might encounter problems when running latest apps.

The iPhone 3GS takes the normal (full-size) SIM card, so you will have no problem there. The only problem might arise from the iPhone being locked to another provider, in which case you will have to get it unlocked.
In general you can use the same SIM card in any make of phone accepting the same size of card.

I don't think so you can use your Sim in any handset. Yes there's some Handset which is locked and in that handset you can use only one sim which is already exists when you purchased these types of set from the market.

Have not been told things exactly right. It depends on what size SIM is used in the Samsung phone, I'm guessing a standard size SIM. The 3GS also uses that size SIM so that wouldn't be the issue here. What would be though is if the iPhone would be able to accept the SIM. If the iPhone is on a different carrier, most likely AT&T in this case & say your phone is with T-Mobile, then it wouldn't work, or at least it wouldn't until you get the phone unlocked.