Hi Helen, welcome to the forum, you will find theres a couple of us support reps from other ISP's floating about all of who will be happy to help if you have any specific questions.
Do you mind if I ask how big the support team is there?
As for the issue about customers own servers thats a little vague, customer could have a server that basically acts like a router sharing the internet out for the rest of the network. They could have a web/mail server. The best advice is to focus on the product that you provide, so is their broadband up, is their connection in sync and authed. Once you can demonstrate that the service you provide us up and working, then you can help them diagnose where the problem may be on their setup (if your work allows you to do so).