Data usage because of A-GPS - deactivate?

[Biffz]

Hi,

I have a XZ1 compact and usually data usage deactivated. The usage statistics in my phone say "zero". But sometimes I have costs for data usage on my bill.

My best guess is that this occurs because of usage of A-GPS. How can I deactivate this? Or what's the best workaround to avoid this?

Thanks,

    Christoph