Adjustment of Status - I-485

Today I called Uscis 1 800 number to ask why after been approved on august 29 2017 and having written proof about my approval my status online has not updated and also I haven't received a welcome notice or my green card even though the IO told me I would get it in about 7 days or 2 weeks. The customer service representative told me that it might take from several months to a year to get the green card in the mail even Though I was approved. I really don't know what to do, I have 3 letters that the IO gave me confirming my approval, I have already scheduled an infopass for September 29, I will take the 3 letters that were given to me. I don't know why it has to take too long to get a green card even though I was approved on the spot, even my file was stamped several times with the word approved. I'm really sad now, I don't know what to do.

Has anyone gone through the same experience? I would like some advice.