<prompt> Human: I moved earlier this month from Michigan to North Carolina and used an Interstate moving company. When I signed the initial paperwork in April, I agreed to a tariff rate of 1000 section TR. On May 16th, I received my final bill via email from our customer service rep with the quick note of Thank you for your business. The .PDF was attached and my credit card was charged for the full amount on the very same day. On May 22nd, I received a phone call from our customer service rep who said that they made a clerical error and accidentally calculated our bill with a tariff rate of 1000 section 03. This means that I owe them an additional 600. As a follow-up, the customer service rep sent an email with a new bill where he openly admitted in writing to the mistake in their accounting department.Is this even legal for them to contact me and expect me to pay more money? I understand that I signed the 1000TR tariff rate, but do I have any legal obligation to pay for their clerical error? Should I just stop whining and pay the additional 600?  <response>: If you have in writing the first amount they charged you, and you have paid that in full, your obligation is done. Youve have paid the amount they said for the service they rendered. 