Hi Toby162,

We have successfully used a product Control Phreak to block incoming nuisance calls. While designed to stop PBX hacking and toll fraud it also will kill unwanted incoming calls as soon as they hit the Panasonic. Retail price is $495 including on-line installation, training and 24 hour support. This is an approved Panasonic product and verified by Panasonic Japan. This has solved this type of problem every time.