I used to use "BT OpenWound" as my ADSL provider, and once in a while I'd have to call their support line.
"Hi, I wonder if you can help me? My ADSL modem's synchronising, and I've got link at the ATM layer, so the DSLAM's working and the VCI/VPIs must be right, but I'm timing out on CHAP authentication, I wonder if you're aware of a problem with your RADIUS server or something like that?"
"Errrr, have you tried rebooting?"
"Errrr, yes actually, only because I knew you'd ask, but that's not going to solve this sort of authentication issue, is it? I've also dumped the PPP LCP frames, and it looks like I'm able to negotiate the first few frames fine, you issue a CHAP challenge, but I get nothing after I send my CHAP response - no ACK, no NACK, nothing. It's pretty obvious the problem is at your end, specifically your authentication pieces? I'm still using the same auth credentials after a reboot, right?"
[long pause] "What's the error number you're getting?"
"It's not a number, it's 'LCP: timeout sending Config-Requests'"
"Can you click on 'Start'..."
"No, this is a Linux Operating System"
"Oh! Sorry sir, we don't support Linux!"
"NO! I'm not ASKING you to support Linux. *I* support Linux. I write Linux kernel modules for fun, for goodness sake! I'm asking you to support this skanky ADSL service that you allegedly provide, and that I foolishly pay you for! ARGH!"
Needless to say, as soon as I could, I switched to an ADSL provider where I could talk to a qualified networking engineer, not an untrained droid with a script. They don't "support Linux" either, or indeed "support Windows". They expect you to be able to look after your own stuff, and they look after theirs. They cost just a little more (not much), but it saves a lot of time and so much agro when...
"... I wonder if you're aware of a problem with your RADIUS server or something like that?"
"Let me SSH in and see, one second ...[pause]... Hmmm... OK, that's odd. I'll restart FreeRADIUS ... Is that any better?"
"Yup! That's done the trick, I'm back on-line. Cool. Many thanks, Simon, owe you a beer!"
I've since moved to Canada, and thankfully managed to find another ADSL provider with a clue. They have never been down for more than a few minutes, so I've never even needed to call them, but I have exchanged a few emails where I can use phrases like "reverse DNS" and "static IP address" without being told "no sir, but we can provide you with a dynamic service at no extra cost" (no thanks, Bell).