Stock sales: FIFO or not?

At the end of October last year, I sold some stock. The stock had been purchased multiple times over the last several years, and I did not sell all of my shares. I knew which specific shares that I wanted to sell, to minimize the amount of taxes that I would have to pay. According to the TDAmeritrade website, they said that shares are sold on a FIFO basis, unless I sent them a letter of instruction indicating which shares I wanted to be sold. So after I sold the shares (but still the same day), I faxed them a letter. A couple days later, I received an email from them saying that they received the fax and that they would keep it in my records. But I was just going through my old statements, and I noticed that the statement that I received at the end of November has a section called "Positions Closed This Period." It indicates that I sold my oldest shares instead of the shares I had indicated in the letter that I faxed. If I have to report my sales on a FIFO basis, then I will pay more in taxes. I followed TDAmeritrade's directions for indicating specific shares, so can I just ignore what the statement says? My fear is that if I get audited, they will look at the statement, and I will be screwed.