>>8
I keep hearing this bandied about, but it doesn't make sense that it would work once you turned the phone off. In order to activate, the phone would have to receive a message over the cellular network. But the phone doesn't ever power up its radio or associate with the towers when it's off!

>>7
If you're paying with credit/debit then your carrier already knows about you. If you pay with cash then you're suspicious (since this is how drug dealers operate) and likely to be subject to law enforcement scrutiny because of it.

Realistically, you should just accept that your carrier knows about you and keep it in mind when you turn your mobile on, keeping it off or not with you most of the time.
Or be like Stallman and don't have a mobile.
Either way isn't suspicious and won't attract the attention of the authorities.