The QWERTZ layout is used in several different countries as standard instead of QWERTY. If you have a QWERTZ device there's no way to change it to QWERTY.
http://en.wikipedia.org/wiki/Qwertz
The technical reason for this is because the letter z appears much more frequently than the letter y in German and other Germanic languages. On French and Belgian BlackBerry devices, the keyboard layout will be AZERTY.
It can't be "fixed". If your device is a QWERTZ then it's going to stay that way even if you swap the keypad the device will stay with the Y & Z keys swithed. The only way to have it as a QWERTY is to buy it that way...