You can not change the PIN code for XM cards. You can not reset it by yourself either.
In this case, you need to contact your XM account manager and he/she will reissue the PIN code for you.
Reissuing process will cost 50 units(USD or EUR) for
- Reissuing the PIN code(30 units)
- Delivering the PIN code to your post(20 units)
For more information, please contact XM support team.