The values provided for amps and voltage are maximums per the manufacturer. It is not uncommon for a switch to have a different rating at a lower voltage, but it should not be assumed. In most cases, if a switch has multiple ratings they will be listed on the switch, or in the manufacturer's documentation.
The thermal stress on a switch is a function of the amps no matter what voltage is applied, so there will be a limit to the amps any switch can carry. Opening and closing creates arcing and mechanical forces that can vary based on voltage and current, and type of load. Stay within the rated value(s) for the switch.