My Main contractor did not charge me extra when he plaster up the wall made by my A/C contractor.

But your A/C contractor need to at least cover all the opening until the red brick level.

If all already plaster smooth smooth, hack and redo again sure the plaster contractor have the right to charge (especially area are large)

At least ask them plaster until the red brick level, or leave 1/2" before the smooth wall.