Airtime not transferable

We have a contract with vodacom. Lines have been locked due to payments in arrear. The past Friday, my daughter received R200 airtime from my sister on one of the contract numbers. My sister was unaware that the number was blocked. I contacted vodacom several times but they are sticking to the same story that they cannot access, refund or transfer the R200 from my daughters number to a different vodacom number. Its extremely difficult for me to believe that this is impossible to do. The only way vodacom can supposedly do anything, is if we pay the outstanding amount on the account. We are not in a position to do so. My child has nothing to do with us being behind on the account. It is her airtime that was given to her. Not ours or vodacom's. Can you please assist me in this matter.