Hello,the truth is that you can unlock the phone ,but you can't unlock all phone for free.The payment sites are very cheap you could try it out and see.You can the link below to unlock .

Note: unlock is not free, You will be charged to get your unlock code.
The only way by which you can get the unlock code for free is by calling your service provider and requesting for your unlock code.

If you service provider refuses to give it to you, then there is no other place where you can get a free unlock code.

Visit the links below if you are interested in buying the unlock code:

mobile-unlocker.com/samsung-a837/rs2wp9/

and


superunlockcodes.com/unlocking-services/rs12wp6/


Good luck.