Duration for transfering extra balance to bank account

If I request to cancel my prepaid card now (letter sent on 04/25/23), then how long will it take for the extra balance to be transferred back to my bank account?

Since I will be leaving Germany on the 30.04 , and I will also deactivate  my bank account on that same day,  I need the leftover balance to be transferred as soon as possible (so I can withdraw it from my bank account).

o2_Giulia, 28.04.2023, 20:45, moved from O₂ Prepaid to English O₂ Community: Mobile