You have to be careful not to assume the technical skills of the end user. What is simple for one can be complex for another..agreed.
if in a similar case, I always get one of my technicians to call the customer back and stay in touch until the problem is resolved.
I am not one for threats and anger so I sent a polite reply to Wheelies expressing my disappointment with their reply and have now been passed on to someone else who has given a more appropriate response..