One company I worked for was moving offices - not far - about 5 miles but into another telephone exchange area. We paid BT the usual arm/leg/unborn child for a new 'high-speed' link (about 10MBit which was pretty high speed for the time) and a frame relay circuit over the top.
All was proceeding swimmingly until BT actually went to install the new circuit and it didn't work. Much panic ensued as we'd given notice on the old office and all the senior management were coming over to open the new swanky office.
I noticed that, next to the comms rack in the new building, we had an unused ISDN32 box and contacted BT who assured me that they could get it up and working in less than 24 hours - which they did. So, the evening before the grand opening, I spent quite a few hours (slowed by both a raging migraine and the presence of a *really, really* annoying Belgian colleague who kept asking me whether it was working - he had ambitions to become European IT boss if our manager ever left but we'd all assured HR that, if he ever did, we'd all be tendering our resignations) configuring dial-on-demand between the new office and the old office over the ISDN32 (luckily we had capacity at the old office too) so that we could use the leased line there. I even managed to get it to add and drop channels according to demand.
I was quite proud if it - especially as I was working off the manuals, never having done it quite like that before (although I'd done linux dial-on-demand but that was quite different from doing Cisco on-demand dialing and bandwidth management).
Since we were on a different exchange to the old office, it didn't count as local calls. Which meant that the 3 weeks that it took for BT to fix our leased line cost quite a bit - although BT did waive a portion of the cost in compensation for not delivering the leased line on time.
 Even using Sumatriptan it's not much fun trying to do techie stuff while if feels like someone is banging a tent peg through the left side of your brain. Fortunately, I was in the comms room and could control the light levels (although said Belgian kept complaining it was too dark) so the photophobia didn't kick in. And I managed to get into a techie-fugue where I could ignore almost anything except the technology.