They already have the permits under that callsign Block which is the problem. Reading through any flight plns through the region, they have their approval numbers for each country listed which are cross checked. For example, there was/is a cargo mob running between Afghanistan and UAE. They were 'banned' when flying under a certain flight number but the same aircraft (south african regos), same pilots with just a different callsign (numbers remained the same) and they were fine. Same with certain military callsigns. Told they can't come in calling themselves XXXXX95 but if they change to YYYYYY95, come on in as that is what the approval for. On a semi related note, I had a half dozen Belgian fighters rock up and they were told that they only had approval for 5 so rack off. Guy doing the comms told me quite bluntly that they were putting six on the ground at either the military base or the international airport right next door in the next five minutes... approval for the six appeared a few seconds later.