The Postal Manager at Black Hill LPO provides the number 13 13 18 as the contact for customer service at Aus Post suggesting they were to blame for serious service errors.
The number however isn’t Aus Post and is a scam number apparently. Horrified that this guy provides the number but worse is the postal service manager at one of these local postal offices subcontracted out where there is apparently no scrutiny of operations or accountability as is with non local post offices. Be aware and perhaps be best to avoid Black Hill LPO Peel Street Ballarat 3350.

Got a scam email purporting to be from Australia Post and the 131318 number was given as a contact. Fake email address and Australia Post number. Do Not Call or click the attached link which asks for payment of fees.

"Priority Mail Express Confirmation Number
Dear,
We regret to inform you that the package you will receive tomorrow will be returned.
This can happen if the recipient's address is wrong (wrong shipping address).
We have extended your shipping time by 24 hours. Pay your extra fees online to submit a new delivery request."

The 131318 number is Aus Post national call center. It's on their official blue tick twitter page. But beware If a suspicious email has it because clicking it could redirect you. The number is legit but I wouldn't click it in a email

This number was on email that looks very convincing, about wrong address, on a parcel, supposedly from Aus Post. Scam

My complaint about the 13 13 18 number was from an email telling me

Received an email saying Aust Post had a parcel for me but the address was wrong. Looked legit but as I wasn't expecting a parcel looked up the phone number. It's a scam so don't click on anything or give any information to these scammers. This is not a Aust Post phone number.

Caller: letter,

letter, very official looking and authentic, claiming insufficient postage and a demand for $2.60, which included a service charge of $1.50! Envelope and enclosed letter all look authentic.