Overcharging Account

MBD has overcharged my account by R1700. I paid R3900 to their account to settle an account and they claim not to have received it because my reference was my name and not my I'D number. Even though I have sent a proof of payment multiple times. They even acknowledged in a call that they received it but not with the reference. They now owe me R1700 because they refuse to cancel my debit order.