Duplicated Debit Order

Nedbank debited my account twice for my home loan payment. Instead of debuting R7038 they took R14076 from my account. I called the call Centre and was only told they will reverse 1 debit order and the money will only be available after 5 to 7 working days. This is an inconvenience for me since I wanted to make some payments only to find that my account balance is low. I'm very disappointed and I've been Nedbank client for 20 years. This reflects a level of incompetence from their side.