Strictly speaking, this is generally impossible unless it is you who provided them with the PIN. The probability of this happening is very low, but in case that it does occur, do not hesitate to contact Paysafecard customer support, who will handle the issue for you.
If someone has learned your PIN number there are several actions that you can take to prevent them from using your money. One would be to immediately spend the entire balance, which might not be the perfect solution. Alternatively, you can always use the Paysafecard mobile application or website to freeze your card’s balance and make sure that no one else uses the money other than you.