We get these in the UK all the time. Usually either try and hold them on the line as long as possible (if bored) or tell them to "fuck off" straight away.
Obviously there's a fine line to tread between playing dumb enough to keep them on the hook and playing too dumb to be useful.
(Haven't had one of them call since, alas: refining your technique is hard if you don't get enough practice calls.)
For me, the most frustrating part of the experience is that regardless of what you say, they follow their script to the letter - they're like method-actors which never get out of character. Just once I wanted them to say "ok - you got me!" but alas - apparently not having a PC or Windows is not enough to sway them.
I cannot writing my own read!
So I login to the router admin page and sure enough it tells me it's unable to establish a WAN connection, modem lights also indicate that it's not getting a connection either.
So I call technical support hoping that they will check and tell me if there is an issue with the service in my area.
They ask me to reset modem and router, so I say "yes, tried all that" they make me do it again anyway. Ok , well that doesn't work so I ask if there is any problem in my area.
Instead they want to dig around in my computer's network/firewall settings. So I tell them the problem is that my router can't get a connection out to the WAN. Lady on the other end doesn't really know what a WAN is but I've already told her that the modem light that should be on is off.
Still they insist on going through the troubleshooting steps on my PC and can't proceed until they've done that. The only computer in my house at the time is my Ubuntu box so they insist it must be that and I have to call them back from a Windows or Mac computer.
So I call back, pretending to have a Windows computer in front of me, pretend to go through all of their steps to no avail. About 45 minutes later she gives up and checks the service status. Sure enough, there is maintenance in my area which is why my internet doesn't work.
But honestly, do you know the level of computer knowledge of 90% of callers to the tech support line of residental ISPs? Requests like "is it plugged in?" or "turn it off and on again" do help lots of people who don't know about these things.
What's worse is often people think they know about computers (and actually don't), and then ring up tech support. This is why "I know computers, I know it's not that" will never work with tech support. For every person who says that & knows computers, there's people who say it and think that (say) the IP address 192.168.1.2 must be on the 2nd port on their router (because the .2 means second port, see?).
Just accept that you have to go through the motions.
Some of these spoof there CLID, and use VOIP dialouts alot as well, so you need to log time and duraction of the call as well as the CLID presented. Any other details you can obtain from them like pretenting you want to do a instant BACS transfer of money to them or need to call them back etc to get more details the better.