BB Curve :: 8900 Unknown Charges On Bill

My daughters boyfriend gave her his old Blackberry Curve 8900, after he got a newer blackberry on his contract. My daughter just used her old sim from her old tmobile phone. I pay £15 per month for her to have 600 minutes and unlimited texts.But since using her sim in the BB, there have been strange charges appearing on her statement. She doesn't use any apps on there, and hasn't seen anything happening on the phone so we're at a loss as to what these charges are.They are only a few pence, but last month it came to over £7 and this month in just 3 days the total is already £2.She popped into our local tmobile store and was told that BB's are not supposed to be used without a data package, whatever that's supposed to mean.Tmobile do a booster for unlimited internet for just under £5 but I can't really afford to be paying that every month, i'd just rather get rid of these extra charges all together. [code]