For us, the most frequent issue on our land line are out-of-country calls (so out of jurisdiction) trying to sell duct cleaning services. We've gone as far as booking a couple of appointments to identify the local businesses that use these providers, but nothing comes of the reports. Where the origin is foreign, there are still avenues for domestic enforcement but authorities appear uninterested - to me this is an easy way to increase the effective cost of foreign call centers that don't obey local laws.