Should be nothing to set, you can enter a 2M channel followed by a 70cm channel without changing anything, just entering the correct frequencies. Unless you've got a bug in the CHIRP version or a glitch in the radio perhaps?
In CHIRP, open the stock configuration for calling frequencies. Delete the ones the radio can't handle., leave the 2m and 70cm channels as they are, and see if you can download that to the radio. If you can, CHIRP and the radio are good and you're entering the freqs wrong somehow. If you can't download that to the radio--there's a problem in the radio or CHIRP version.