2005 Nissan Micra automatic gearbox issue


i have a 2005 nissan micra 1.2 auto.only 37,000miles on the car

2 days ago i started having acceleration issues maybe relating to the gearbox.

Not sure

on the auto the gears change to higher gears automaticly if pressed hard to go faster or up hill but for some reason its just flat, it dosent go in to a higher gear at all.

I feel like it just changes through all gears but does not recognise when accleration is being pressed for a higher gear to kick in.

can anyone please help.
i called a mechanic, and his 1st answer is to change the gear box.