Metro Manila (CNN Philippines) — It's against the law to discriminate between card and cash payments, the central bank reminded retailers and customers.

"Maliwanag naman po sa Consumer Act: Kahit anong method gamitin mo to pay, it should be the same price," Bangko Sentral ng Pilipinas (BSP) Assistant Governor Johnny Noe Ravalo said during the launch of Consumer Welfare Month on Friday.

[Translation: It's clearly stated in the Consumer Act. Whatever method you use to pay, it should be the same price.]

Most of the consumer complaints the BSP receives is about card payments, Ravalo said.

Some retailers impose a surcharge for customers who choose to pay by credit card. Others do the opposite, offering a discount for those who pay with cash.

"Whether it's a surcharge or a discount it contravenes the law. It says whether I pay with my card or with cash the price should be the same," Ravalo said.

He urged affected customers to take down the details of the product they intended to purchase and raise the issue with the store manager. If the store doesn't want to give them the fair price, they can file a complaint with the BSP.

The central bank has received about 33,000 customer complaints from January 2009 to date.

Ravalo said another common complaint involves unauthorized withdrawals and transactions with their cards.

He reminded consumers not just to keep their cards safe but also their passwords secure. "Even if you lose your card, thieves won't be able to use it if they don't have your PIN (personal identification number)."

However, weak passwords are common, Ravalo said. They're usually the cardholder's birthday, the word "password" and a number series like "1234."

Card payments are still little used in the Philippines. Of the 2.5 billion payments made every month, 99% of them are made with cash or checks. Only 1% use credit or debit cards.