My bank did a double withdrawal of $2000. (years ago). It was settled ON THE PHONE in 15 minutes. You connect directly to the manager and/or the President.
Years ago I wrote check to the bank holding my mortgage. They posted the credit to the wrong account and in the wrong amount.
An intermediate bank then processed that check for the wrong amount and passed it on to my bank, which also posted the transaction with the wrong amount.
When I first brought it to the attention of my bank, the clerk really didn't seem much interested and wanted me to take it up with the first bank.
I said to her, "Then all I have to do is close my acount today and I'll be $500 richer? That sounds like a good deal." At that point the clerk and her supervisor took more interest.
The solution was relatively complicated because all three banks had to agree to make properly consistent adjustments to undo the error.
After the matter was cleared up I changed banks.
This may work for smaller financial institutions, especially if it is locally owned and operated. However, we're talking about Barclay's, one of those "Too Big to Fail" places from about 10 years ago. Trust me, I worked for one of these TBTF places until they decided to purge a lot of us high-paid 55+ people for a bunch of 20-nothings who would work 16 hour days for half my salary. Four years later and I still get upset when I think about the circumstances...