I have been a long time customer and a Mileage Plus Club member. On a flight to Mexico earlier this I was filling out my immigration form. As the female flight attendant passed me by I did not hear her ask me for a drink. As she passed to the next row I held my hand up where she could see me, and she did. She ignored me as she served the others behind me. I then touched her shoulder with my indexed finger, again I was ignored. As she walked away down the isle I gently touch her on her back with the palm of my hand. She whipped around and told me not to touch her. She said I had ignored her as she had first passed. I explained to her I was filling out the form and did hear her. I told her she did not have to be so rude, I merely wanted a glass of water . She abruptly laid down a glass of water down in front of me. This was witnessed by other passengers and the other flight attendant. I was ignored for the rest of the flight. I was angry and wanted to complain but I felt it would fall on deft ears, I was also fearful of being met in Mexico by authorities. United has not had the best reputation in addressing situations with passengers. As I de-planed, the the observing flight attendant, rather than wishing me well as they normally do, she bowed her head down looking at the floor and said nothing. As I said I would have written a letter, but I have friends who have done so just to be ignored by an airline. This was an isolated incident and I continue to fly United, but I felt like management should know. If you care to call, I would be happy to discuss the incident. Sincerely, John Arnolfo