South Australians are being warned to steer clear of a shutter business after the consumer watchdog revealed it had failed to refund customers thousands of dollars for work that was never done.

Consumer and Business Services said it was investigating Sam Branco of Mates Rates Shutters and Blinds following numerous customer complaints.

Commissioner for Consumer Affairs Martyn Campbell said customers reported being owed “significant amounts of money for work that never progressed”.

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He said the probe was launched after the watchdog received complaints about the business, including a failure to supply products within a reasonable time and a failure to refund consumers thousands of dollars for work that was never undertaken.

Campbell alleged Branco had gone door-to-door soliciting business while being unlicensed to do the work.

“Not only is Mr Branco unlicensed for this type of work, but the contracts he is entering into don’t appear to comply with the protections under the Australian Consumer Law that apply to unsolicited consumer contracts,” Campbell said.

“CBS is treating these allegations seriously and actively investigating the matters raised and will take appropriate action,” he said.

In response to the allegations, Branco told 7NEWS.com.au he was taking necessary steps to rectify the issues.

“We have hundreds of happy customers and I am learning to do things better and above board when it comes to licensing and contracting etc,” Branco said.

Campbell encouraged customers who were in contact with either Branco or Mates Rates Shutters and Blinds to contact CBS to assist with the ongoing investigation.