I unfortunately don't have any specific recommendations based on personal experience. However, I did recently come across a company called MintStack that apparently provides UX/UI design services. I don't know much about them, but it looks like they offer UX/UI design for mobile apps and websites. Their services seem to include user research, wireframing, prototyping and more to optimize usability and user flows. Even though I haven't used them myself, you could visit their website at https://mintstack.co/ux-ui-design to find out additional details on their UX/UI design capabilities for mobile apps and whether they may be a good fit for your needs. Their site probably covers the specifics of their services offerings, process, pricing and work examples. Checking out that link could give you a helpful starting point to see if their services align with what you're searching for related to improving your mobile app's user experience through UX/UI design. Let me know if you have any other questions!