My friend gave me his iphone cause he didn't like it, I'm using optus sim card it's been 2 months and everything was ok. few days ago it became locked.

I can still use 3G to connect to internet but can't receive calls or make calls, if any of you guys had same problems please let me know how you guys deal with it thanks

Call Optus. From another phone.

What should I tell them?

What you just said above.

Where did your friend get the iPhone from?

Well he's gone back to overseas I beleive it used to be a telstra iphone, but he got it unlocked. but what happen now is the iphone can read the sim card and even using the 3G funtion but just not calling and answering

Try another Optus SIM to test. Maybe it's your SIM/barring.

tried it didn't work and a voice when tried to call told says the phone has been blocked by optus network

Then there is your answer. Talk to Optus about this or find another phone.

well what I don't understand was why it was working fine but next min it's blocked I called them and asked they couldn't tell all they said was because the phone wasn't under my name....

It was probably working fine one minute because they didn't know about the ownership. Then they discovered the issue and blocked it. The phone stopped working after that once they enabled the block.

Transfer ownership if that is the problem. It sounds like you know about the problem but you're unhappy that it happened to you. Nothing you can do about that besides buying your own phone or getting it fixed by talking to the original owner. I don't see how somebody else using the iPhone is a big deal - people lend phones all the time and purchase on behalf of family members, etc. Maybe they think your iPhone has been stolen.

This forum isn't Optus helpdesk so you're better off talking to them (again).