it seems to be a genuine mistake, and perhaps a doctors letter to verify you have been for a operation and also suffer depression will help you ,the council will probably accept full repayment,or even instalments i think the genuine people who claim benefits seem to be targated more then the fraudsters ,do not worry as it will probably be the end of the matter if arrangements to pay back are made hope this helps the council dont know what they are doing from one day to the next ,i think it is a total waste of time telephoning them