Watch CM apps others are having adware issue associated with them, true caller is a good app though. Another way is to go to call logs, tap on the number you want to reject, tap 3 dots in top right corner then select "reject call" which applies to that number only. In the future when a call comes from that number yours will ring once then reject it. What I like about true caller is it has a database of numbers associated with spam and solicitors and automatically blocks those. It really has cut back on the number of bogus calls. You can also request to be on the do not call list for solicitors.