Trailblazer 2014 engine problem

Hi sir kindly help me in from the Philippines
we bought a car brand new from the shop
then after 2 years it was quite working
good but unfortunately today it has a
problem on engine It can't over take even a
trike or a motorcycle with a side car with
full throttle gas pedal and the engine is
having a hard time accelerating to 2,500
rpm even when neutral gear is on also my
car is suffering this when we suddenly stop
but sometimes it works the best but
sometimes it doesn't it was checked by the
service center but they can't see the
problem because it was working well but
after they check it out it went worse again
my trailblazer is like having its own volition
how to address this can this be a factory
defect please help please email me I'm so
depressed with this car:(