I have an iPhone 4 on 5.1.1 (jailbroken). While I succesfully activated FaceTime on my device, whenever I try to call an iPhone 4/4S owner I always get 'FaceTime failed'. I had a person FaceTime me with his iPhone 4S and he said that it was dialing correctly but I never got a call. I restarted my device (both soft and hard reset), restarted my router but I had no luck. For the record, my iPhone has been bought on Greece (also my current residence) but I have signed in from my American Apple ID. I thought this may have been the reason for my issue so I went to Settings>Facetime>Apple ID and changed the location to Greece. Still, no luck! I also tried adding "126.96.36.199 and 188.8.131.52" on my network's DNS but it still didn't work. Help would be highly appreciated! Thanks!