Two points…
The data is data, how it’s represented is only relevant to you not the system (unless it’s a hex string).
It gets sent to the device as binary ‘data’ in any case.
The second point is - be careful if you’re letting users set the radio frequency - on several levels.
In most countries only one or two bands are legal for unlicensed comms. If they step out, and interfere with some other service,the penalties can be extreme.
Also, the antenna will often be different for different bands, affecting the range.