I deal with nuisance calls as a very small % of my day to day.
There really is no point in firing into the phone monkey at the other end of the line, you may have a bit of fun at their expense (or so you think) and are able to regale your tales to your compatriots on how you pwned some minimum wage knob-end by winding them up (well done you!). Fair enough, they may terminate the call, but they very seldom remove you from any dialler or database under their control. If anything they'll up the frequency of calls to you (I know I would if I was being paid a bowl of rice a week and fed crud from some random who thought he was smarter than me).
If you don't want to go down Bronto's route
You could purchase a standard phone which you can allocate certain ring-tones to friends and family. That way you can choose to ignore calls from unknown numbers.
Your Service Provider (SP) will have a Nuisance Calls process, but more often that not it does precious little to stop the calls.
I would suggest using the following websites to identify which SP the offending call originates from:
UK Phone Info
Magenta
These sites are pretty accurate and should identify the range-holder responsible for the number making the calls.
I would suggest taking a note of the following and presenting the info to the responsible SP:
At least 3 x calls with times and dates of when the calls took place (this is time sensitive, as it can result in either detailed (<10 days) or basic (<30 days) traces being carried out)
Number receiving the calls
Number making the calls
Nature of calls e.g. PPI, accident claims, silent, scam, phishing,vishing etc.
Calls of an obscene, malicious, or threatening nature should be reported to your local Police in order that thay can take the issue up with their SPoC (Single Point of Contact) and liase directly with the SP responsible.
Another option is to ditch your landline. I pay for mine, but it hasn't has a device connected to it for a few years (I pay for it, and in doing so have procured a pretty sweet deal for a stable 150+ mbps to t'internet.
Please note that a lot of the phishing calls I see are from offshore via Skype, but now that Skype have been taken over by Micro$haft, it makes it easier to deal with calls of a similar nature.
Hope this helped...if so, giumme a thumbs down