iphone 4 disabled

hi all i bought an iphone 4 2nd hand from a collegue from work around a month ago which he said was unlocked and jailbroken,as i didnt have a sim for it at the time until now i didn`t check it,(he doesn`t work for use anymore so cant get money back)i now have a sim but all the phone says is connect to itunes iphone disabled,i cannot access any part of the phone to find out the firmware etc of the phone,
is there a way of unlocking/jailbreaking it myself ?
thanks for any help or advise