It is possible, but there is no need to. Your journeys by bus, tram and metro will be on your monthly bill as well. A balance is not needed and actually mostly useless. That is why there is an automatic refund on your bank account. When you check in during the weekends, you will be charged for nul cents. When you check in in a bus your card will be charged for the actual price. Weekend vrij can be used all week and it automatically recognizes the  way you  travel. Remember that travelling by bus in the weekends is not free. 

To be more specific, the balance that was on the card will be subtracted from the invoice after the first month. Since the subscription costs are higher than the balance, it will only be paid out on talianathoo's bank account if the subscription is cancelled; if the subscription is kept, talianathoo will pay 21 euros less for the second month.

Oh ok. Understood for the refund. Thank you. Now concerning the fact that even on weekdays the subscription is still working. Could you please explain this? I read that the subscription was only valid for weekends and not weekdays, how come I am not paying on weekdays too?

Whenever you travel on weekdays with Weekend Vrij, you will be charged full fare. These will be billed once a month on top of the subscription price and will be charged from your bank account. Thus, you don't need balance on your OV chipkaart anymore.

Thank you so much for your help! So the 21€ that was left on my card and the additional amount of money there is to pay will directly be billed to my bank account? 

That's correct!