Monarch Dental review: Endless circles and no explanation

People, be careful and check all invoices from the company Monarch Dental Assoc. My son visited the orthodontist twice and the first visit was only consultation, which cost about $300. The second was consultation and he provided some services, and he told that the visit was about $600. So, the total sum was $900, but they sent the invoice for $1, 200. For what they took this sum? The doctor refused to speak and advised to call to the reception, but the lady refused to explain.