When they print your CEWE product for you they use an automated print system so they print the data exactly as they receive it. The data they receive for your product is stored as a 'read only' file which means they can view your product but cannot make any changes to it themselves. If they reprinted your order the same spelling mistake would still be there.
If you are not happy with your products then you can return them to them under their guarantee. Once they have received your order back they can then issue you with a voucher so you can make any necessary changes and then re-order your product.