Citizens Bank

I transferred my money 2000.00 from my savings to another account and the transfer said completed.
I went to the bank and withdrew my 2000.00 with no problem, a few days later the bank made an addition 2000.00 deposit and withdrew it so called no one could give me an answer after bring put on hold for almost an hour then I discovered there was a deposit return I have no knowledge of so now the bank has put a hold on all my accounts stating I owe 2000.00 because the transfer did not post because it was a holiday and they were back log and I didn't have the money at that time, then how was aloud to withdraw money at the teller if I didn't have it! It's an inside scam going on I no people who were employees and told me a few stories on how they rip off there customers with these fake deposits and transfers citizens bank your a fraud and u will not get away with it!Feji and Trevor