Stu got a new phone number for his iPhone and he keeps getting calls about paying a student loan. How can he prevent the phone from ringing on unwanted calls? Leo says that he can get a Google Voice number and then use it to filter out the phone calls that aren't in the contact list. He can also use an app called Nomorobo. or True Caller to filter them out. Lastly, he can block it from the carrier itself, but these calls often change the caller ID to thwart it.