Benq M555

i have benQ m555,the problem is network lock(at&t)  i found unlock code from this http://www.mobile-unlocker.com/ ,thing is i have two choices software/code which is safe and better coz some one telling  code dosent work sometime, meanwhile if i go for software i might lose datas, this was some one suggestion who i met last week, so i need a concrete suggestion about which has safe and good.