What phone number from the order does EasyRoutes use for custom SMS notifications?

EasyRoutes will attempt to use the first available phone number in a stop's Shopify Order in the following priority order for sending a custom SMS notification:

1. If the order is a Shopify Local Delivery order, the mobile phone number entered into the local delivery checkout shipping method input field (e.g. with the default instruction text: "We may use this number to call or text you about your delivery.")
2. The phone number as seen an order's Contact Information section:
   1. This is usually from when a customer provides their phone number instead of an email as the contact during checkout. This can be enabled in your checkout settings. (Settings > Checkout > "Select what contact method customers use to check out." > Phone number or email)
   2. Orders can also be edited to include a phone number in the "Contact information" section afterwards.
3. The phone number in the order customer's profile (alongside their email address in their customer profile)
4. The phone number in the order's shipping address, if available.
5. The phone number in the order's billing address, if available.

As it appears on the Shopify Order page:

If you require more specific behavior you can enable the "Send SMS to shipping contact phone number if available" checkbox in the SMS notifications section. This will make EasyRoutes only send SMS notifications to the phone number listed in the shipping address (#4 in the above example). If no phone number was entered during checkout, no SMS notification will be sent. You can require customers to enter a shipping phone number during checkout in your Shopify checkout settings.