...To be safe you could try and pull off the road...
I wouldn't be so sure about that unless you pulled into private land to which the public did not have access.
The Land Transport Act interprets a "road" as being "a place to which the public have access, whether as of right or not" so even if you pull off the road and that place you pull off onto is not a designated car parking area (and which strictly speaking may still be a road, so there! ?), such as would likely be the case on a non-urban road, then if you remain in the driver's seat you must be still driving on a road, not parked .
I am quite certain that is the law, as it is written in "black and white" and so therefore completely beyond dispute and must be applied; good sense must be thrown away in its interpretation and application. And the law is never an asss (extra "s" to get around the forum's naughty word filter filtering out the name of an animal ) is it?
On the other hand lets remember that the definition of a road doesn't always matter. The ban is on a driver while driving, so it doesn't matter whether you are on a road provided you are not a driver driving. As I mentioned a few threads back presuming this comes to court, this is the only plausible out for the driver given the totality that I've read about, bearing in mind IANAL but i find it difficult to see it would work. (As I also mentioned if the phone was mounted there is an out for the camera but not the reading an SMS bit whatever claims he may make about not unlocking the phone or faulty advice from NZTA that he didn't actually know at the time. Although, and I cannot remember if I mentioned this before I guess the OP could claim he wasn't sure whether he got an SMS or a phone call or what and was checking to see. But if he knew it was an SMS or continued reading once he realised it was an SMS then this defence would also go down the toilet.)