Labor Inquiry about Salary Change

I wish to clarify with your assistance in this field of expertise as I am experiencing a very difficult & tough challenge right now wherein I cannot decide whether to complain or not.

The story starts here, first, I was hired and given a monthly salary rate of P 15,000.00/month with a working schedule from 9 am to 8 pm during Monday to Thursday and 9 am to 6 pm during Fridays last December 10, 2015.
And then as we are working we noticed that there are discrepancies on the report of payroll, others are staying only from 9 am-6 pm and Mon-Fri which is 40 hours only.
Then, our department head complained, proposed and seek approval to have an increase which is approved and granted by our CEO. Which is, according to book 30% which is rendering 48 hours or 6 days. But due to wrong computation, it was not 30%. Mine was 15,000 then became 17,750 which is not an increase of 30% dated March 1, 2016 but the salary adjustment was applied April 11, 2016. And, as time passed by, I was regularized. I got an increase based from 17,750 to 19,250.00. And now, a memo was issued that our 9am to 8pm will be changed back to 9am to 6pm. making it 40 hours a week.
But as an effect, also, salary will be decreased on my end, from 19,250 to 16,500. Since the effect of increase is only because I will not be rendering 48 hours/week anymore. Is this okay or allowable?

If ang basic salary is the same or higher and they are just removing extra hours, pwede yun. (i'm assuming that the 8 hours removed was classified overtime). I'm also assuming that all this wasn't specifically mentioned in your employment contract? Kasi if meron specified in your contract then that should govern

ahm. Fair po ba un samin? We rendered 48 hours before and almost same rate sa 40 hours lang. then nagpaApprove kami tapos nagrant na existing na.. aun they want to take it back daw po.. as a chain effect. ibababa ung rate namin na involved kasi naman po is ibababa na ung hours of OT namin. qng icocompute naman po sa dapat na OT na 30% un kulang na nga po ung "increase/adjustment" dahil sa pagrerender ng 48 hours a week tapos po ngaun na ibababa na daw nila dahil idedecrease naman ung hours na irerender. so Okay lang po ba un and fair?

sorry, wala akong naintindihan dun sa last na sinulat mo.
Paki ulit. nalang ang be specfic,
example: 1. from july 1, 2015 our daily rate is P600 pesos.
2. We worked 8 hours of overtime every week that is why we got an extra P750 per week. Isa isa lang. you don't need to write everything you want to say sa isang post.
3. on december 2015 they ......

Just to summarize if ang basic pay ay hindi binaba. Binawasan lang ang hours of overtime and walang nakasulat sa employment contract na merong guaranteed number of overtime, eto ay legal.

If ang binaba ay yung basic pay iyan ay illegal.

If nakasulat sa employment contract na guaranteed ang OT, pag tinanggal nila yung OT eto ay kelangan parin nilang bayaran.

Okay. Una po.. 15,000/month.. but our schedule was 9-8 pag Mon to Thu then 9-6 pag Friday.
a total of 48 hours per week. Nagcomplain po ung head namin kasi may mga co-employee kami na 9-6 lang Mon to Fri a total of 40 hours and same rate or higher than us pa po.

naitop up po sia sa basic. sa computation ng adjustment na un. naiAdd siya sa Basic pay. not sa OT

It is being presented as part of Basic Pay. Not presented as OT. tapos po aun. naregularize ako and ang basis ng computation nun is sa 17,750 na (adjusted amount). Nagtaas sa basic again which is 17,750 to 19,250. Now they issued a memo stating irereduce ang hours which in effect ibababa din ang rate po.. bababa sia from 19,250 to 16,500.00