Is there anyway to factory unlock my iphone 4 for free?

My bestfriend gave me a iphone 4 but I need it factory unlocked to use it.

Assuming you don't know someone in the business of unlocking phones, the only way to get it unlocked for free would be to request it be unlocked by the original carrier. Most developed countries have laws requiring cell phone carriers to unlock phones if they're purchased outright or after the contract has ended. One notable exception is the United States. Because you are asking this question, I'm going to assume you live in the US. If you live in the US, then you (yourself) likely won't be able to get it unlocked for free. If your friend is still with the carrier they purchased it from, then you can have them call that carrier and see if the carrier will unlock the phone. The carrier will almost certainly not unlock it if you are not a current or recent customer. Since there are no laws protecting consumers in the US, you are at the mercy of the carrier and their policy or whim as to whether or not they will unlock it for you for free. If your friend has satisfied the contract they purchased the phone under or they bought it at full retail price, then the carrier will probably unlock it for them for free, but this is not a guarantee, they don't have to if they don't want to, and they really have no motivation to do it if your friend has already cancelled their service.

Before you go through the trouble, only an AT&T, T-Mobile, or Northwest Missouri Cellular iPhone 4 can be unlocked for use with another carrier. The others are incompatible with other networks other than their home network. The carriers that offer the iPhone 4 that can't be unlocked include Verizon, Sprint, StraightTalk, Cricket, Virgin, Alltel, C-Spire, and all others not listed above.