Habitation tax

We pay a monthly habitation tax of €14 a month. This has just been increased to €32.17 a month.

I have a few questions I was hoping I could get some advice on:

I am trying to get a contact for the tax office in Carcassonne, to ask them why there has been such an increase. I have not been successful so far.

I also want to confirm whether we should be paying this tax at all, as some owners I have spoken to say that they do not pay it. As far as I was aware, this is a mandatory tax. I read that if you do not occupy the property and it is let on a furnished basis, that you may get an exemption from paying it...does anybody have any further info?

Thanks!