i bought my phone from a small time developer who had a develpoer account with apple... so how can i check if i am signed up with apple??

Your iPhone won't have the Dev Account; The UDID stuff is handled by the AppleID of the purchaser. Unless he sold ya that account too, then you're not signed up with apple :)

unless he specificaly put your iPhones UDID into his list then it wont work.

easiest way: try to upgrade