Open Question: Invalid SIM for iPhone 3G?

Submitted by Anonymous on Sat, 05/14/2011 - 00:54

I am on a plan atm with optus this 1 >> http://www.optus.com.au/store/phone/nokiac503
I pay $19 a month , free facebook and stuff If i terminate this it costs almost $300
I just bought an iPhone 3G from ebay and i put my sim card in, it is unlocked for optus but my sim isnt compatible or something it says "Locked Sim". Im really upset because i cannot use my new phone and i cannot afford the iphone plans

Is there a way I could get my SIM to work? or a cheap Optus plan?