Outstanding refund

On the 16 January 2019I went to deposit R2000.00 to my first national bank account at the Lenasia branch ATM, just as i was busy with the transaction the system went offline and the slip came out saying the transaction was unsuccessful. I immediately went inside the bank to report it and i was made to fill in the form as the person who opens the ATM comes in certain days mind you that money was the registration money which was closing on Monday they told me they will get back to me in 3 days. i waited for 2 weeks when i got a message form fnb with the refund of R1700.00 and i immediately went back to the bank to ask i why was the money short with R300.00 and i was told that is the money they have found in the ATM. I spoke to the manager who promised that they will investigate and get back to me in 14 or so days up until today i never received neither phone call nor money back im still waiting i want my R300 back im now scared of depositing money in their ATM in case same thing happens