The Cutoff frequency of bandpass filter
The results Multisim gives you are correct. You can check it by using this calculator.

The cutoff frequencies are calculated by analyzing the circuit and seeing which part of it is responsible for low-/high-pass and calculating the corresponding frequencies. Check out this website for a detailed explanation!

As to the results you got from a website, they seem to be wrong or misinterpreted - your center frequency is only 2.2 kHz, but f1 is 20 kHz and f2 is 2.4 kHz - the range doesn't even cover the center frequency.