Unlock S3 with 4.4.2

[AC Question]

I just recently updated my S3 to 4.4.2 KitKat and I'm currently with Rogers. However, I'm looking to switch providers and need to unlock my device. How would I go about doing this without spending any money and without rooting my phone? I'm a bit skeptical with all the websites and video tutorials I've seen so far. Any help would be appreciated!