Thanks Guys for the answers.
Are you guys from Europe? I forgot to say that I`ve heard it happens in Europe . My question came because I have a friend who flies for a chinese company and as we know their english is quite poor. And then he was saying that very often their are given codes starting with 7 because this is an unoficial way to let your coleagues ATCOs know a flight which requires special atention were on its way.
I heard that and didn`t believe that much because I had the idea codes were given by computers at Eurocontrol.
A320