jon, its not about the money left but i have to use that number for a sms bank transfer validation.
I have that problem myself sometimes. At my bank it takes a week for a new number to be used, for anti-fraud reasons.
I notice on your profile that you're in Germany, which makes it difficult to recharge the card. You can do it online (if you have a PESEL) but if the sim card has timed out through not topping it up, you'll only be able to receive calls in Poland rather than Germany, probably due to roaming costs.