Unlock your Siemens mobile
Siemens - Together we'll make it talk
Many large networks like O2 or Vodafone always lock their phones, so you can only use it on their network, unless you desided to unlock your Siemens phone.
In most cases you can do it without a need to flash your device's memory but simply via remote unlock codes, postal unlocking, or via remote logs.
Most of the time it is not only possible to unlock your Siemens phone but you can also do it for free. There are plenty places on the internet where you can download free software calculator programms that will generate a free unlock code for you.
And be sure it is as legal that you unlock your phone as it is that you give it away, lose it, break it, leave it turned off, or do anything else with it! In other words it is perfectly legal because it's your phone.