1 month from Cape Town central to Durbanville post office

A letter posted at Cape Town Central post office on 14 October 2019, was placed on my post box in Durbanville on 15 November 2019. Unfortunately, I had to reply to the original letter by no later than 15 November 2019 - not possible!! At the same time an account from the City of Cape Town dd. 14 October 2019 was also put in my postbox on 15 November 2019. The due date for the account was 8 November 2019 ! How am I supposed to pay it BACKDATED ?? It seems that the post office is saving up postal articles at the Durbanville Post Office and only delivering once a month !! Shocking service