Worst service ever

I have been paying my loan of which only 1 month was in arrears, A consultant called me and an arrangement was made to double debit the following month on the 25th. A debit then went off before the agreed date 15th January. Now I have to go through the admin of reversing that amount and then they tell me they will refund the money in 7 days. On top of that, I still get bank charges for reversing that money of which that was not my fault but the bank itself. debiting my account without my permission is *****. this is by far the worst experience iv had with any bank