In the web servce I say
public List GetCustomers()
{
PR1Entities dc = new PR1Entities();
var q = (from x in dc.Customers
Because that's how a list serialises. Your Customer class on the client side has been generated from the service metadata, which effectively describes how it's serialised not how it was originally defined. If your original Customer class is available, you can specify to re-use it in the client code when you generate the service reference, and then it will come through as a List.