Data Sense comes bundled with GDR2, it does not exist as a separate download link like Nokia apps. Are you using a carrier locked device??
and how many updates have you had for GDR2??
Some people have reported that if you hard reset a GDR2 build it can sometimes bring Data Sense back. However, some carriers are taking Data Sense out of their final builds when they're sent OTA. It's a bit of a lottery, really.
Who is your carrier? You appear to have an Italian rom but are youy isoimg am Italian carrier? Check with your carrier to verify whether they are allowing data dense or if they are blocking it!