If you want to reset service light or oil service on a Opel Astra G, Zafira, Corsa, Agila all by yourself, this is what you have to do:
STEP 1: press on the right button from the dashboard until…
STEP 2: …you turn the key in the second position (while you keep pressing on the button)
STEP 3: turn the key off
If you want to check if the service light / oil service was corectely reset, turn the key in the second position and see if the “InSP” message still appears on display.