Did you read this section? Don't know that your answer is there however. Do you have a owners manual? It should be helpful. Any chance the radio did not come factory installed?
Since you are not from the US that might figure into solving the issue too. See if you can figure out what model radio is installed.
Audio/ Video/ Navigation / Electronics Discussion
Nitro Year: 2007 (1 of 91,815 sold in 07)
Nitro Model: R/T 4X4 Stone White
CAT-BACK Exhaust, CAI, Projector Head Lamps
Fully-Equipped w/all factory options