I also have the phone compartment/booster and I have no hard numbers to back up my impression that it does help strengthen the signal. When I received my "welcome" package from Porsche USA, there was a card in there reminding me to register my booster with my carrier. It uses the VIN as the serial number and has a manufacturer listed (I believe). The registration has nothing to do with function. Apparently it goes back to earlier boosters that were sometimes overpowered and the requirement is in order to single out a malfunction booster and contact the owner. This is my understanding. I thought I got the web address for registering off here, but I can't find it now. So it is good it is listed. I originally Googled it and book marked for when I got my car delivered.Look forward to your report on whether it makes any difference. But how can you confirm that it wasn't working before. I ask because it appears that "activation" is simply filling out a form. My Cayman also has that option but I have never confirmed it was doing its' boost thing (or not). BTW, I also have AT&T and applaud your tenacity for dealing with - how best to put it - dipsticks. I don't recall receiving any info from Porsche about registering the booster. What sort of info was provided?