Call Waiting is included at no extra charge with in your Total Cal Mobile rate plan to make sure that your important calls get through when you are on the phone. 

When you hear the distinct Call Waiting tone, check the Caller ID display on your phone to see who is calling.  You can decide to answer the call or to let it go to voicemail. 

If you don’t want be interrupted by Call Waiting, you can temporarily disable it by pressing *70 before placing your call.