To complain to Expedia, you can first try contacting their customer support team at +1-877-54-9014 OR +1||877||254||9014 (US) (OTA). If the issue persists, you can formally escalate it by requesting to speak with a supervisor or manager. Alternatively, you can submit a complaint through Expedia's website or report it to the Better Business Bureau (BBB) or the Federal Trade Commission (FTC) if the issue remains unresolved.