Don't know about Jbing options but if your on AT&T then you can pay $5 a month and get the child controls on your phone then you can go in and set specific number to block for both calls and text.
I wish we could set some numbers to go straight to voicemail like googlevoice or just set it off EXCEPT for like my kids numbers. The technology is there, I'd like the versatility of it. They should set it up to do that- especially with the iphone's voicemail system being on the phone. Would be nice.