Registering a Signal Booster

[Reg]

In the gift from Porsche that was recently sent (book, pen, card), there was a letter than mentioned that the car has a signal booster and that

Before use, you must register this device with your wireless service provider and have your provider's consent

Has anyone done this with ATT in the US?
Does it not work unless registered, or is it that they just want you to register for some FCC reasons?

Thanks

Sponsored