Looking for top-notch mobile app development service

I am in search of high-quality mobile app development services and would appreciate recommendations. Specifically, I am interested in companies or agencies that excel in creating robust, user-friendly mobile applications. Key factors include expertise in cross-platform development, particularly using frameworks like React Native, Swift, and Kotlin. I am also looking for insights on companies that offer comprehensive services from initial consultation and design to development and post-launch support. Any success stories, client testimonials, or examples of their work would be highly valuable. Can anyone suggest top-notch mobile app development service providers?