As long as humanly possible, they're not getting a penny out of me.
I say "as long as humanly possible", because they have the money to supply electricity at a loss for several years, to undercut and then buy out all the other energy suppliers... but I'm hopeful that won't happen.

Kill switches for stolen phones means kill switches for all phones.
Who is in control of the kill switch?
Given that people store banking stuff, train tickets etc on their phones, it means you can be left penniless and stranded if the phone suddenly stopped working.