A service provider generates a customer key and a merchant key for facilitating efficient provision of assistance, by the merchant, with the customer's shopping and payment, via customer-merchant key coupling. When a customer approaches or enters a merchant's store the customer has signed up with, the user device carried by the customer wirelessly broadcasts a signal for the customer key unique to the merchant key. When the merchant server picks up the signal, the service provider communicates to the merchant server information in the user's profile including identifiers, shopping preferences, or the shopping history of the customer, subject to any user-created restrictions contained in the profile so that a sales clerk of the store may approach the customer to give recommendations, suggestions, or other assistance with shopping, based on the information.