Annoyed with invitation vendor - WWYD

Soo...I paid my materials fee.

I added a few services and I asked for a revised service quote. She realized she made a mistake on the materials fee and without saying anything just added to my materials fee.

I wrote to her and said I signed a contract and as far as I'm concerned my materials fee is paid in full. WHat I got back is below. I'm kind of annoyed. It didn't automatically recalculate. She noticed it and changed it without saying anything to me. If I hadn't added more services, I would not have gotten a new invoice and would never be paying the fee. WWYD?

For some reason, on your original quote, the price of the white micah paper was $0.00 instead of $0.50. It must have readjusted itself when I recalculated your invoice just now.
As for signing off on a contract with the materials fee set at $492, the fees are not part of your contract. The contract is contracting the company to do your invitations and outlines what your (and my) rights and regulations are regarding the services provided. There is a paragraph that pertains to the price quote, saying that if an error is made prior to you paying your materials fee, I will notify you immediately and send you a revised quote. I've just realized I have nothing in there that pertains for errors noticed after the fees are paid, so there isn't anything that, necessarily, forces you to pay the difference and there isn't anything that, necessarily, tells me the difference is forfeited. Furthermore, the only obligation I have in bearing the responsibility of noticing an error is in producing an accurate quote...there is no language that tells of your responsibilities after receiving the quote. So, we've got a quandry...

I guess I'll leave it up to you and what you think is right. I know what I would do if I were in your position, but it would not be ethical of me to force that upon you in a client/vendor relationship. It's a loophole, plain and simple. If you feel justified in taking advantage of it, then you are free to do so.

:)