SA Post Office
Incorrect Post Always Received

Just a quick one, we live in a house with the number 12, behind us (not in a complex) is a 12a and a 12b. All the houses are accessible as it's not a complex, however whoever is delivering the post seems to be too lazy to deliver 12a and b's mail to them as it keeps getting dumped in our post box.
Please could you ensure that your postmen deliver post according to the house numbers.
Thank you