Finding and using your net promoter score

I was buying mobile phones again last week. Not to feed my tech habit this time, just cos my son threw one in the paddling pool. All very straightforward, courtesy of the Carphone Warehouse, but I wasn't expecting a text an hour later asking me One Question about my experience in buying the phone: on a scale of one to ten, how likely would I be to recommend Carphone Warehouse to a friend?
Now I've had a pretty good grip of net promoter scores for most of the brands I've worked with in the last couple of years, so I've commissioned people to ask this question a few times, but I've never been on the other end of it. It does make you think about your experiences of the brand (all pretty favourable in this case). And that led my cynical side to wonder whether brands that have an automated NPS tracking system in place for every transaction make more effort to deliver recommendable experience, or if it is more likely that it is only those that understand the importance of creating advocacy amongst their customers that bother to monitor NPS. Either way, it really impressed me. I meant to post about it last week, but to be honest forgot about it until I saw this ad on the tube today (you'd think with a new phone I could learn to take photos with it......)
Another Telecoms company, Plusnet, proudly letting me know that 8 out of 10 of their customers would recommend them to their friends.... which sounds like distilling the output of an NPS study down into an easily digestible headline as well. This category, traditionally one of the worst culprits for abominable customer service, seems to be paying more attention to brand experience....which can only be a good thing for people who keep having to replace their phones....