Band selection is a client decision, however, you can modify few settings and push client to prefer 5G radio over 2.4 G.
Band steering and Band balancing are two available option.
These two features are covered well in below article (though it refers ZD but feature works similarly for Unleashed)https://support.ruckuswireless.com/articles/000002338
If this issue is only happening with your Samsung Galaxy then try creating a dedicated SSID and broadcast it only in 5 G radio, but keep in mind that 5G radio will have a smaller coverage area then 2.4 G.
Syamantak Omer | Community moderator | Staff TSE | CWNA | CCNA | RASZA | RICXI | Follow me at https://linkedin.com/in/syamantak-omer-5949b6124