Now it is easy and simple to delete all the contacts in your blackberry mobile at an instance. Just follow the steps given below.
Note: Steps given below suits for other Blackberry device too.
Step 1: Download BlackBerry Desktop Software from WWW.BLACKBERRY.COM and install it.
Step 2: Now connect your blackberry mobile to your computer. (BlackBerry Desktop Software will detect your device automatically)
Step 3: Click Device as shown in the screen shot.
Step 4: Click Delete. Delete device Data dialogue box opens.
Step 5: Select Selected Data->Address book – All and click delete.
Thats it !!!