why can't I make the customers bill to the same as the name so it tells me that it is already in use

HI Ann

Customers don't have bills they have invoices, suppliers have bills, if it is telling you 'the name is in use' it means you already have the same name in use, you cannot have exactly the same name in customer & suppliers.

So if you have an entity that is a customer and a supplier of yours then you have to alter one of the names. i.e Hacksville Pty Ltd (customer)   Hacksville (supplier) or Hacksville Pty Ltd - s