Horn buttons on the steering wheel

Hello,

Does anyone have any ideas on how to remove these plastic parts from an airbag steering wheel in a Golf Mk3 without breaking them?
The "How to..." book says "simply pry it out."
With a small screwdriver, it makes a cracking and squeaking sound, but doesn't budge even a millimeter.
What am I doing wrong?
(I don't want to damage the airbag unit either.)

Greetings,
Thomas.