Do we use increase or decrease

Do we use increase or decrease when we want to ask something about AC and anyother common way of sying this in USA/UK:
"Increase the AC temprature its cold".

"Decrease the AC temprature its hot".

I don't think we use either one here.

"Turn up the A/C; it's too hot in here."
"Turn up the heat; it's too cold in here."
"Crank up the A/C; it's too hot in here."
"Crank up the heat; it's too cold in here."

To me, "A/C" is the cooling portion of air conditioning and "heat/heater" is the warming portion of air conditioning. They are often two different units in houses here, although they can use the same air ducts if the house has central air conditioning.

If we are talking about adjusting the temperature I think we usually use "thermostat":

"Turn up the thermostat; it's too cold in here."
"Turn down the thermostat; it's too hot in here."

If i just say ,"Turn up the Thermostat its very cold or "Turn up the Thermostat its very cold here" then will bit be grammatically correct or I have to say
"very cold IN here" ,why do we say "in here".

turn the sound down/up
turn up or down the air conditioner?
air conditioner
turn the air up = warmer or colder?
next time you turn up the AC
down.

There is plenty of material to read in these threads
Many of the suggestions appear ambiguous when examined in detail, but are probably perfectly clear in context.

I've closed this thread in case it might turn out to be another long one that duplicates what's been said before.