No they won't unlock it because you aren't a customer...I'm sure your friend didn't buy it out right....so that means its still got a lengthy contract...even if the friend bought it from someone else...most people sell iPhone that are bought a Hardware Upgrade to make some easy cash.
two options:
1) Use Gevey....but it has issues as Rogers tries to verify visual voicemail via texts....I don't recommend it because it costs you each time...I experienced it and ended up just selling my Rogers iPhone 4S as it doesn't play nice...even after extensive research and plenty of trial n errors with editing APN and carrier.plist files from the iPhone's internal file system.
2) break the iPhone slightly....pay $149 or w.e and get a replacement(make sure it has warranty)...since you are in USA they will hand you either a AT&T or a Factory unlocked replacement...essentially giving you a 100% working iPhone 4S for as little as $200...since your friend "gave it to you"...
Goodluck, please note 'follow either of the above mentioned options at your own discretion, I will not be held responsible for something that doesn't workout for you' no will I provide support on 'How to' do/go ahead with any of the two listed suggestions.