If you pay taxes of your salary at Chabber, despite having a tax exemption card, it is very likely that you are receiving study grants (SU).
If your SU is occupying your tax exemption card, you can't use this for your salary at Chabber and you will have to contact the department of study grants i order to make them 'release' your tax exemption card. From there, it will be possible for you to attach it to somewhere else as well.
So try this, before doing anything else.
Have a good day!