Want to buy a blackberry 81**/83**/88** on eBay or having problems with your blackberry, here are some tips that may help.:
1) Check whether it is locked or unlocked. If it is locked to a specific provider, please consider the cost to buy the unlock code. Unlocking a blackberry 81**/83**/88** on T-mobile/Orange/O2 would cost you around £20-30. The unlock code for vodafone network is cheaper, you can buy the blackberry vodafone unlock code on ebay for around £5-10.
2) Check the variants and understand the main differences:
8100 - Blackberry pearl, has a camera, no GPS, no WiFi
8110 - Blackberry pearl, has a camera and GPS, no WiFi
8120 - Blackberry pearl, has a camera and WiFi, no GPS
8300 - Blackerry curve, has a camera, no GPS, no WiFi
8310 - Blackerry curve, has a camera and GPS, no WiFi
8320 - Blackerry curve, has a camera and WiFi, no GPS
8800 - has a GPS, no camera
8820 - has a GPS and WiFi, no camera
3) If your blackberry is asking for a password (not an unlock code) and you don't know it, just enter random characters when it is asking for a password (until 10 attempts). After that, the blackberry will erase all the data and you can enter a new password. If an IT policy had been pre-installed before you entered the password, you wouldn't be able to receive/make calls/text. To fix this, just do a search on google to find an instruction to remove the IT policy (enter keywords: removing blackberry IT policy).
4) If your blackberry has a frozen white screen with one of these error comments: 102, 513, 507. You need to re-install the operating system. To fix this, just do a search on google to find an instruction to re-install the operating system (enter keywords: install OS blackberry or JVM error 102 or JVM error 513 or JVM error 507).
Disclaimer: this tips is for guidance only. If you need to do point (3) and/or (4), please do that at your own risk. I will not be responsible for any lost or damage.