A
I imagine it depends on what facility you're using to block callers. I use a program called NameID myself, and it has an option to either simply block a caller and completely ignore them, or automatically redirect the call to voicemail. Perhaps you have something similar?
I believe it's only for MetroPCS and T-Mobile customers. Came pre-installed on my phone. But I see similar apps on the Google store.
There's a $2 additional charge on my MetroPCS monthly bill to take full advantage of all the features. YMMV.