The reason I'm getting this phone is because my old samsung phone just bit the dust and does not show anything on the screen anymore. So I've been looking on ebay for a replacement phone and the 7105T looked promising.

The only concern I have is that right now I'm on a T-mobile service plan, and i was wondering if there is any fees attached in using the Blackberry 7105T, making it inoperable when putting in my existing SIM card. Or will the blackberry work straight away when i put in my sim card?

If you have a Blackberry Data Plan it should work straight away, just pop your SIM card in and go! Without the right data plan your 7105t won't do anything more than phone calls and text messages. No email, no web browser. But those functions will work without any plan at all, no extra fees either.

You also need to change device in your bis ( change pin & vin #)