At the end of the day...
A company's main purpose is to make money for it's owners, regardless of what business it's in.
o2, like all the rest are out to get more for less. Other companies have a product they can tinker with, Mars Bars are lighter than they used to be, Kit Kats seem to have far less chocolate on their bottoms than they used to.
I once replaced a car with a newer one of the same model, supposedly higher spec, but things in the older car had been replaced. (soft touch plastics replaced by hard ones, grab handles replaced by blanking plugs, etc)
All making tiny savings per item but when you add them all up it'll be a substantial amount.
o2 can't exactly give you 59 seconds for your minutes airtime, so they cut costs by reducing staff.
I'm currently an o2 customer and have had little need to contact them, same goes for when i was with vodafone & T-mobile. Only switch because of flashy offers of freebies at the time (i know i'm a tart). Let's hope i don't need to talk to them any time soon.