Your colleague is quite right. What you are seeing is not the rate at all. It is the total cost based on the billing block and the duration of the call.
By simply looking at you data, I see that your buying rate is 0.055 and that you are not using any connection or disconnection charge and most importantly, you have a 60 seconds billing block. The 60s billing block will allow to compute the costs by rounding the duration to the next minute. So based on your call data, here is what we get for the buying costs:
Code:
Real duration --> Rounded duration --> Formula = Result
01:07 --> 2 --> 0.055 * 2 = 0.110
00:05 --> 1 --> 0.055 * 1 = 0.055
00:12 --> 1 --> 0.055 * 1 = 0.055
05:41 --> 2 --> 0.055 * 6 = 0.330
00:33 --> 1 --> 0.055 * 1 = 0.055
00:18 --> 1 --> 0.055 * 1 = 0.055
00:18 --> 1 --> 0.055 * 1 = 0.055
P.S.: On the customer interface, the actual rate ($/min) is displayed in the CDR. The CDR is a little bit different than the admin CDR.
Cheers