Apparently from recent glowing reports, turn around has been only a week for some.
I suppose it depends which service centre you send it to. Where are you located, find the nearest one.
I'm sorry you are having difficulties, here is the link to get the process started. http://www.dji.com/support
Have you done an IMU calibration on a perfectly flat surface? Have you done a gimbal calibration?
Are your antennas pointed in the correct orientation?
If you are flying in a neighborhood, your Phantom is on 2.4 which is the same as almost every WiFi router in each home.
can you try in a open area free of interference.
Does the WiFi signal strength meter drop down as you lose video signal?
Pretty much this. File ticket, they send shipping label and you pack it and ship it. I would recommend including all of your documentation and a letter advising what the issue may be.