And 5 cent Hershey bars used to be about twice as heavy. Time marches on, so do schemes.
That is definitely underhanded, though - in the US, I'd consider that a unilateral change of contract (meaning it was void) and switch carriers. (And probably get an attorney to find another few customers willing to join a class-action suit and turn it over to the appropriate law enforcement agencies. New York City got into trouble for something like that - moving the pay day up by one day a month for 14 months - we lost a pay period and when an attorney just filed a motion of intent to sue, everyone got an extra check.)