Many phones (including all Nokia, Samsung, LG, Blackberry and Siemens) have a limit on how many times you can enter an unlock code. The limit is usually three attempts. After the third attempt you will no longer be able to unlock this phone using any unlock code. Your network provider and the manufacturer will be unable to unlock it. In many cases on the third attempt your phone will be permanently locked to that network.
Erase All Data: Many free unlock codes work by exploiting a bug in some very early versions of phone software. They provide you with a code that will remove the network lock by erasing all the data on the phone. This works on less than 2% of many phone models. If you happen to be in that lucky 2%, it means you have an unlocked phone but no contacts, messages, emails, ringtones etc. However if you are in the unlucky 98% your phone will remain locked and you have lost all your data.
Void Warranty: Nobody cares about their warranty until they need it. By unlocking your phone using software or using all the unlock code attempts you will void your warranty. You don’t want to lose your warranty and have to purchase a new phone.
Unusable Phone: The worst case scenario is you use unlock software that renders your phone unusable. This happens a lot more than you might think. If you use a free unlocking service which renders your phone unusable, there is nothing you can do. Your phone provider, phone manufacturer or phone insurance will not cover you for the damages or repair your phone. You will be stuck with a repair bill, wasted time, and a locked phone.
Don’t risk your investment in your phone, use a safe secure carrier or manufacturer based unlock service like Travelers Mobile.