Dispute not resolved after 60 working days.

Since 27th june I logged a dispute regarding my returns assessment. Was told it takes 60 working days for it to be resolved. 60 days came and gone, I made follow up calls and the only same thing told was by all agents is " I will escalated your matter, for it to receive priority as 60 days passed" it is now 10th working day after that 60th day still the matter is not resolved. It takes them a day to make a mistake and overlook documents, maar to fix their error, we are told to wait for months.