What is the customer service number for costco? How to call Costco: use the toll free number below to contact customer service for help with orders and membership questions. When you call, you will be asked the questions below. 1-800-955-2292. Thank you for calling Costco.com.What is the toll free number for costco? To place an online order with Costco, go to Costco.com and browse the webpage for items you want to purchase. Click the Add to Cart button next to any item you wish to buy, then click the Cart, and finally click Proceed to Check Out to place your online order. When placing an order,...