KLM's 24-hour rule: Passengers are allowed to cancel their booking within 24 hours from the time of purchase for a full refund. This policy is applicable for all fare types booked directly with KLM. Assistance: KLM Customer Service: Assistance from a representative is available by calling [(UK) +1 (𝟖𝟎)𝟒𝟖𝟓𝟑𝟗𝟎𝟎𝟏 0r (USA) (+1-𝟴𝟬𝟰-𝟴𝟱𝟯-𝟵𝟬𝟬𝟭)] ¹. from the US.