Call Blocking

We are fed up with nuisance calls on our landline.  These average 4 - 8 per day. Now looking into having one of these fitted.  

Initial visit, and our line is suitable for this service.  I spent this evening writing out a long list of family, friends and organisations we are happy to receive calls from.  Hopefully it will be installed within a week or two.  

Anyone out there using this already, and have any feedback comments?