Michael Donaldson, 58, said his experiences of the call centre began after a salesman came to his house.
The sociology and psychology lecturer, of Plains, North Lanarkshire, asked him to assess his bathroom.
He said: "He started off saying it would be £19,000, by the time he finished it was down to about £6000. We asked loads of questions like if they had their own workers. We were quite happy to go ahead as we thought we were getting a reputable company.
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