This is a great app for Yes customers. I dont get GSM connection at my workplace but I do have Wifi. This app gives me the ability to make and receive calls on my cell even receive calls from my standard GSM number via call forwarding. I already pay for Yes credit for internet at home and I have thousands of unused minutes in my account because I only use data. I have also previously used this while travelling, making calls home to Malaysia at various airports that provide free WiFi connectivity.