The chemical reaction between sulphur dioxide gas and gaseous ozone is best represented by the equations as

${\mathrm{O}}_3$ is an oxidising agent which oxidises others being reduced itself.

So, it oxidises sulphur dioxide to sulphur trioxide by the reaction,

$3{\mathrm{SO}}_2+{\mathrm{O}}_3\to 3{\mathrm{SO}}_3$