First arrival and annex 49

Hi,

I received my annex 46 to work in brussel and my visa and I d like to understand how to registrer in order to take the annex 49.

Its said that we have to take an appointment 8 workin days max after the arrival, but i was told yesterday by an agent of the city hall of brussel that its not the case anymore and that i have to send them an email with my passeport scanned with the stamp of the aéroport.

Should i believe the internet site of brussel ,or the agent ?

Thank you