Absa gave authority to another bank to withhold my money without verification

I had a bad experience with Absa and I have been banking with them for years. I checked my bank balance on the 28th of March and I saw that an amount of R19305 was missing from my account. I went to absa 3 times that day and no help. The ***** dept said they received a complaint from Nedbank and were told to withhold these funds. Nedbank said they have paid it into my account and Absa cannot even see that amount as an income. Now I’m sitting with no funds and I have debit orders coming through. They are telling me it will take 15 working days. How is this my fault when they didn’t even verify that the information was true. I need to leave Absa