The sim eject hole on the iphone 4 is significantly harder to press in using a paper clip than the previous model, just use bit more force, it'll open no problem.

According to what I can find on this it should remove the same way as the prior iPhones sim card. A paper clip should be a decent substitute for the sim card removal tool that came with the iPhone.

The following article is from Apples knowledge base and has a guide as to how to remove a sim card.

http://support.apple.com/kb/ht1438

there is a dor with a hole holding the sim in

look at the this iPhone4 guide

follow step 8

also ceck out this apple support article

Who doesn't have a paperclip in their tool box??? A very versatile tool indeed!!! Pity it's a conductor... :o)

Thank you, being a little more forceful with the pin did it!

My phone showed no sim, I removed the sim and re inserted it and now it works fine!