Elderly people are unable to withdraw pensions from their local post office because of a faulty phone line.
Pensioners normally use a machine at the Cowley Drive post office in Woodingdean to collect their weekly payments.
They then spend their cash in the nearby shops.
But the machine has broken and they are having to collect their money and shop elsewhere.
Manager Brian Hammond tried to resolve the problem more than a week ago but was told by Post Office headquarters it was a fault on a British Telecom (BT) line and has heard nothing since.
Mr Hammond said: "If they can't get their money here, they can't spend it here."
One woman was in tears on Friday when she found out she could not access two weeks' worth of pension.
An 82-year-old disabled woman said she had had to borrow money to see her through.
She said: "I feel sorry for the staff because the Post Office headquarters don't seem to be doing anything about it. Some people are living hand to mouth while the Post Office and BT push the matter backwards and forwards between them."
Trevor Standing, who has run Trevor's General Store for 16 years, has seen trade fall by 20 per cent in the past three weeks.
Customers have been unable to pay their bills and one pensioner who took a taxi to the post office had to return empty-handed.
Mr Standing said: "I'm concerned about the people who can't get their money. There are a lot of upset people and the worrying thing is nobody seems to want to do anything about it."
A Post Office spokesman apologised to customers and said: "We're trying everything we can to get the system back on line and speaking with BT and the operators who run the system."
A spokesman for BT said: "Our records show we're not the broadband service provider for this customer but if there are any problems with any BT line then clearly we'll investigate them."
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