Software product line engineering (SPLE) enables systematic reuse in developing various products within specific domains. Several approaches have been proposed to support SPLE implementation. In this paper, we report our experiences using delta-oriented programming (DOP) to implement a payment gateway product line. The implementation has specific challenges because the services of payment gateway are provided by many vendors. Even though they offer similar core services, each vendor often has distinct characteristics that must be accommodated in the product line application. The core services are modeled as similar features in the feature model, but each vendor's implementation might differ. Therefore, the feature selection must address vendor-specific configurations, requiring a multi-level configuration. This paper discusses the challenges and proposes solutions for achieving a multi-level configuration in the payment gateway domain. We also implement the solution as a tool support to enhance flexibility and promote applicability across other domains. © 2025 Copyright held by the owner/author(s).