Press the Menu soft key, select Features > Call Waiting select Call Waiting then press Switch to enable/disable the setting, then click save.
Press the Menu button then select Preferences, choose Call Waiting and press the edit soft key, select soft key, select y/n depending on whether you want to enable or disable call waiting. You can also dial *56 to activate or *57 to deactivate call waiting.
On the handset, push the right hand side of the central four sided button. From the available options choose Select Services then select Call Waiting, either enable/disable this then select Save.
The MyNetFone softphone does not have a call waiting setting, if you only want to answer the current call you’re on you can simply reject any new incoming calls.