MTC Namibia credit gone!

MTC Namibia has 'de-activated' my pre-paid number/simcard - for whatever reason they did find? This is not a big problem, because I can re-activate it [after making a statement at the local Police that the number actually belongs to me]. The BIG problem is - the credit still available on the specific simcard, has disappeared, miraculously. How on earth do they explain this?