Mimimum Charge In Price Model Steps

Hi all,
I want to have a price model as follows:

-if 0<call duration<60 sec, total charge should be 1Euro
-if 60<call duration<120sec, total charge should be 2Euros
-if call duration>120sec charge is 1Euro per minute

What I did was to set a price model with three steps:

-a price model step of 0-60sec with minimum charge 1Euro
-a price model step of 60-120sec with minimum charge 2Euros
-a price model step of 120-infinity with charge 1Euro per 60sec, minimum charge 0.

For the first step its all fine, but when a call is within 60-120sec, e.g. 70sec, I see a charge of 1Euro, not 2Euros.