overpayment

Housing Benefit Overpayment

So,due to a long story with a tenant, in a fully managed property, in December they beware aware that the tenant wasn't living at the property, yet they carried on paying the rent. The letting agent didn't inform me, so everything carried on. The council now want 7 months overpayment, the letting agent didn't appeal and now I've been limbered with this bill of £2800. I've got a possession order and am now waiting for the bailiff to evict them, but they've already left the property, but not handed back the keys, it's being used as a drop-off point for letters and parcels. Letting agent also won't refund their payments for the months of overpayments.