16 000 phone bill

My mom bought a phone at autopage it was an upgrade and decided to take a phone for my sister knowing that she only pay a fixed amount she just took the phone and never asked question and no one explained anything to her. In February it was her birthday month and she got her bonus and Autopage debited R16 000.00on her account and when she asked for the statement she never received it they told her the contract that she took was an open contract still puzzled because she didn't understand the term \open contract \" until they explain to her but still she does not know why they change her contract from top up to open contract now the store have been closed and my mom phone is blocked we do not know who to speak to because all contract they have they transferred them to their specific networks and when we go to Vodacom they say there is no outstanding balance but the phone is still blocked. "