A deaf and partially blind man was left humiliated after a Costa coffee staff member allegedly said "if he's deaf, he shouldn't be ordering drinks".
Mr Sandeep Bhinder, from Uxbridge , visited the High Street branch in his hometown in December 2015 where he ordered drinks by writing them down on a piece of paper.
However, after being mistakenly charged for six drinks, rather than three, sister Simran asked staff members for a refund.
What happened next, she said, was something she had "never experienced".
Ms Bhinder said: "When I asked if we were allowed a refund, the man refused - and there was no manager in on the day.
"He then said 'I asked him, but he's deaf and can't even speak'.
"He was very confrontational and intimidating and when I asked if there was a complaints procedure, he acted as if I was invisible."
Sandeep and Simran, along with Sandeep's wife and their mum left the branch, but Simran returned a few days later.
"There was an acting manager there this time who was sweet, but not helpful" she said.
"When she called the man over in question, he said 'well if he's deaf, he shouldn't be ordering drinks'.
"She didn't do much about it and was just a bystander watching."
The family told getwestlondon they were appalled by the remarks made and were not concerned with money, but more about how Sandeep was treated.
"I think it's outrageous, there was such a lack of understanding and my brother deserves to order his own drinks," added MS Bhinder.
"It has left his confidence shattered and now he won't go out without his wife or me present."
Kerry Parkin, Costa Head of Communications said: "Costa take all matters relating to customer experience very seriously.
"We have launched an investigation into this matter and would like to assure customers that this is an isolated incident and does not reflect our high standards of customer service.
"Costa is unable to comment further at this stage until the investigations have been fully completed”.