Is there any way i can check if my iphone is unlocked for free?

I don't have any spare sims. Its an iphone 3gs

I picked up a few sims on eBay for a few bucks each to test to see if my phones were unlocked. Thay is the only way that I know…

When you can lock your iPhone without restriction, your iPhone is unlocked. You can factory reset your iPhone to bypass the passcode. Here tells you how to factory reset your iPhone in detail:
http://www.windowspasswordsrecovery.com/articles/iphone-data/restore-iphone-5-to-factory-settings.html

There are a lot of IMEI checker in the internet. With the use of your iphone's IMEI number, you will be able to tell if your phone is unlock.

You can check your phone's IMEI number on the settings of your phone.