No refund for your deposit

so 4 months ago i moved out of my apartment and the exact day i asked for forms to cancel the service. they asked for more information and i sent it through to the, but till this day i have still not received a refund. the people in the credit department said refunds only take place 4-6 weeks after final invoice which if they could not see it was IN JUNE . now i must once again go through the same paper work and wait 4-6 weeks once again and they want to DEDUCT AMOUNTS FOR THE MONTH OF AUGUST. how the hell do they do the math? in the meantime new tenants moved in and still they think im also renting there? how can they register 2 tenants at one location without given permission? this service and their stupid staff must be closed down.