You deal with the person who prints your part. There is no account manager relaying a question to a workshop and a workshop relaying an answer back, which is why a design question asked at nine is usually answered before lunch rather than in two working days.
Every job is invoiced, with your purchase order number carried onto it. We are not VAT registered, so the quoted figure is the invoiced figure. New customers settle on completion; account customers work to 14-day terms.
Print settings are recorded against your job: material, colour, layer height, wall count, infill, orientation, so a reorder six months later is printed from the same recipe rather than approximated. That is what makes a repeat order a repeat rather than a new experiment.
Capacity grows with demand. If a job needs more machine hours than the workshop currently has, you will be told the real date rather than an optimistic one, and the answer to sustained demand is another machine rather than a longer queue.