In response to SST,

UA's website reservations are separate from UA as well. Often it takes a call to "Web Support" (which is another name for the independent travel agency "getthere.com" that UA uses). When UA can't get me a voucher for the discrepencies, I often have to call the other number.

The biggest prob with this is that UA (or DL, or any airline) will often tell me, "Oh, the price you got on the web was a web-only fare." Most of the time this is not accurate.