According to KLM Airlines, the facility to change your reservation is quite possible, and that too without any penalty or charge. However, you need to process the change for the KLM flight itinerary. In that case, you are requested to use the online procedure because, under the official site page, guidance for the ticket change is possible and with a much easier and more effective approach. However, to proceed with KLM Flight Change offline, dial KLM's customer service phone number, US Numbers OTA: +1-800-860-5036 or +1-800-618-0104 and then connect with the assistant.