E wallet

I'm very disappointed in how FNB can just transact funds in and out of people's accounts without their concern. I received an ewallet on the 23rd Oct 2019 ND I successfully transferred it into my account. Little did I know that the was a system error that put my account on a negative. On the 27th same month. An ewallet was sent again to my account only now I can't access the funds because of their error that left my account on a negative. I tried contacting the bank several times only to be taken back ND forward. Saying the money is sent back to the sender. When I check the Senders transaction there is nothing of that sort. How is it now my fault that there was a system error. ND I can't access my funds. I called for days till this day I haven't been refunded. I'm told that admin will send it in 24hours. It's been 8days now ND I still waiting for them to fix the error so I can get my money back. Please help