I bought this product last year, it's simple to use and it works. However, what I didn't know (until I sought technical help today) is that you can only block 100 numbers (the box comes with 200 pre-programmed numbers too). We have now exceeded 100 blocked numbers - yes we do get a lot of nuisance calls! - so I now have to reset the box to clear it and start with re-blocking those numbers from call centres etc who haven't given up on calling us.
Such a shame about this as I can't find any reference to it only taking 100 numbers on the Amazon listing or on the manufacturers website. Would have given the product 5* if it wasn't for this :-(