Glen Eira Bayside Crime Investigation Unit detectives are investigating a series of deceptions involving credit card fraud over the past two months, Victoria Police say.
Police have been told three unknown males attended a milk bar on Kambrook Rd, Caulfield North about 4.20pm on 8 June.
While there, the group purchased cigarettes and food using a credit card.
It is believed they manually entered information into the Eftpos machine to manipulate the transaction.
It was later established the sales had not been authorised.
The trio returned to the milk bar a few days later but were refused service.
On 6 July, police believe the same males attended a massage business in Elsternwick.
The males attended the Glen Huntly Road premises about 6.40pm and produced a credit card to pay for the treatment.
They again manipulated the Eftpos transaction to make it appear they had overpaid before the store attendant handed them the difference in cash.
It was later realised the transaction had not been processed.
Investigators believe the same trio attended another small business on Glen Huntly Road, Glenhuntly about 4pm on 10 July.
Once again, they manually entered information into the Eftpos machine, claiming they had paid too much and demanding to be compensated.
They returned later in the day to claim the funds but fled once police were called.
Police have released images of three males who they believe may be able to assist with their enquiries.
They are perceived to be of African appearance with short dark hair and aged in their late teens to early 20s.
Investigators believe the trio may be targeting small businesses, particularly store owners who speak limited English, and are warning attendants not to give members of the public access to their point of sale Eftpos machines.
Anyone with information is urged to contact Crime Stoppers.