The buyers said they were told that the agency had a "special arrangement" with the banks under which it could ensure that the buyers' credit limits would be reduced by the amount of the deposit, but that no actual transaction would take place.

While the documents they signed did state that the deposit would be withdrawn, they said the agency's staff contradicted what was written in the contracts.

"The estate agent was misleading us when she told us that Ricacorp had a 'special arrangement for this special deal'," one of the buyers said, adding that it was unreasonable to expect the potential buyers to read every detail in a stack of documents they were told to sign on the spot. "We felt cheated. It was clearly a misleading sales tactic."

Both buyers, who had the deposits refunded late last week, said their banks had agreed to waive payments. But the buyers said they could have been left with a huge interest bill had the banks taken a different stance.

"Am I supposed to pay the interest for the credit card payment if they cannot arrange a refund before the payment deadline? Will Ricacorp pay it for me?" the other buyer asked.

Buyers rushed to snap up the first 185 homes at The Austin after prices were set at an average of HK$22,871 per square foot, well below market expectations. A six-day registration period ended on October 24, and the draw took place on October 25.

But, after learning that their cards had been charged despite missing out, the buyers say they were among dozens who went to Ricacorp's sales office on October 27 to demand a refund.

The agent signed a written agreement with the would-be buyers that day assuring them the company would contact the banks to arrange a refund as soon as possible.

HSBC, Citibank and Standard Chartered, whose cards the buyers used, said there had been no "special arrangement" with Ricacorp, and that it was up to the merchant whether or not to debit a client's credit card.

Ricacorp denied breaching any regulations and said its agents would have explained to buyers that a transaction would be made if they chose to pay their deposit by credit card, and that their banks might insist on customers settling the payment before a refund could be arranged.

A Ricacorp spokeswoman said the buyers "might have misheard what the agent said". Refunds would normally take at least two weeks.

The Estate Agents Authority said it could not comment on individual cases, but said estate agents had to obtain written approval from buyers whenever a credit card was involved in the payment of a deposit.

Estate agents must abide by the authority's code of ethics, which states that agents must "provide services to clients with honesty, fidelity and integrity".

Taking shape above the Austin MTR station, The Austin is a luxury development of 576 flats by New World Development and Wheelock Properties.

Besides setting prices far lower than expectations, the developers also offered a stamp-duty subsidy to woo potential buyers.