'Snap!' goes the camel's spine

I had an unhappy experience last week with one of my longest-standing employers here.     It's just occasional contract work, you see; and such paltry sums are involved that we had, for some time, been exempt from tax.  A year or so back, they started taxing us.  This was a bit of a pain, since the rates being paid are puny enough already for the kind of work involved.  We were promised that an increase in the pay scale was in the pipeline, to offset - and, hopefully, more than offset - this 20% sting.   I never received any notification about any such change in pay rates.  Lord knows, I've asked often enough - but they never quite got around to telling me.   Anyway, this month was a big month for me.  I did a number of promotional events for them, most of them quite long - so, I should have been in for quite a nice wedge of cash to see me through the holidays.  Something close to 5,000 rmb; over 4,000, even after tax.   But no....  it seems the new pay scale has introduced a strange and superfluous distinction between 'promotional' and 'training' events.  'Promotional' is now worth 25% less, it seems.   Also, the events were all credited as 1.5 or 2.5 hours, and..... well, the pay scale only provides for 1hr, 2hr, or 3hr events; so, in the past, if we went over a whole number of hours, we got paid for a full extra hour (whether we did 15 minutes or 45).  But not any more.  Oh no.  Mind you, it could be worse.  At least they're not rounding down.  But they have invented a "half-hour rate" which is only about 100 rmb, and really not worth getting out of bed for.   Ah, but, that's not even the worst thing.  No, the worst thing is that three of these four events were supposed to have been a full 3-hour duration (that's what I was booked for, that's what I did, that's what I claimed for in my paperwork), and they just arbitrarily decided to whittle them down to 2.5 hours for the purposes of calculating my pay.... without even having the decency to have a word with me about it first.   Were they thinking that I wouldn't notice?  Were they thinking that I wouldn't care?   How WRONG they were!  I won't be working for them any more.