I own a shop and do LA quilting. I have a form I fill out when I take the quilt top and it has specific questions and answers about the top and what batting, backing, pattern and thread the customer wants. It is signed at the time of drop off and if I have any question about what is requested I call the customer and that item discussed. The notation is made and when the quilt is picked up we go over all that was requested to be sure the customer got what they asked for, then they sign the sheet as agreement all was as requested. There is no excuse for the customer not getting what they asked for, other than laziness on the part of the Long Armer not wanting to change thread and reset the tension.
If they are too lazy to do what the customer wants, they should not be doing any Long Arm quilting.