What's your worst post-sales-engagement story?

CS Folks - When it comes to post-sales engagement, we all know how important it is to get it right.

Sometimes though, it can go really, really wrong!

I’m curious, what is the worst post-sales engagement experience you’ve ever had? And how could it have been made better?

And conversely, what is your best?

Please remember - we don’t want to name and shame anyone or any company!!