How to block solicitation calls on Magic Jack

I have friends that have recently installed Magic Jack. They are getting 8-10 solicitation/marketing calls a day. Is there a number to call to remove these people who are calling or is there a code number you can put in to block them. Seems like years ago you could put in *70 or something like that when a call comes through and it would permanently block it. Any help would be appreciated.

Check with Mr. Google. There are several articles. Some say you can and others say not.

Thanks.