Default [Q] Help unlocking S III after 4.3

I have been reading through the forums as much as I can and can't seem to get specific or consistent info. I have a Galaxy S III with Telus, I'm switching to Rogers, don't want to pay their $50 unlock fee. I want to unlock the phone but the 4.3 update is not allowing me to use the option for 4.1.1. And every I look says not to flash a 4.1.1 rom onto 4.3. So how do I a) get back to 4.1.1 or b) unlock 4.3 ? If I could just get a link to the full steps involved that would be great. I'm pretty comfortable with rooting etc. I rotted my Xperia X10 awhile back and that was simple enough. I just can't seem to find an exact answer and don't want to piece it together from several sites. Thanks