Earlier quoted context omitted.
Not sure how long telcos thought they could get away with charging so much for SMS ( http://www.nickloper.com/2011/02/how-much-does-a-text-messag... ) but now that things have changed it looks as though they thought they had other ways of making incredible profits from message transmission. Ha!
The problem is, the money still has to come from somewhere. When income drops in one area (SMS), and costs do not go down, they'll likely have to increase pricing in another area.
However, this increase of course would also have been the case without the new laws (as you say, as people move from SMS to Whatsapp, they have to compensate). The only difference is that they now can't differentiate between different uses of the internet, but only on the amount of data you get.
I don't think the net neutrality isn't such a bad thing price/economic wise. I'd rather have this clear system which might mean slightly higher prices for the average consumer than a system in which different prices for different uses of internet make calculating your actual costs more difficult. In my opinion, that would only give more opportunities to telecom providers to screw you over with little details, rules and clauses in their contracts -- something which history has shown they don't shy away from (rounding up every call duration to a full minute etc.).