Why am I being charged an extra three per cent for using my credit/debit card?

I would like to share my experience as a customer at some of the local mobile shops, and what they all have in common is that they all charge an extra three per cent over the listed price if I wanted to pay using my credit or debit card.

To avoid that they say that I should just go to the ATM and get the money to pay for the product. The reason I want to pay using my debit card is because I don't feel comfortable bringing large amounts of cash in my pocket and the purpose for the cards is to help make people's lives easier and safer. But when the shops say that they charge an extra three per cent for using the card, I feel that it is wrong for them to do so, but they just say it's the company's policy and all the other mobile shops do so.

This sounds like a very unethical way of doing business as the shops are charging us for using the service of the banks which by right is their responsibility to pay. I have never experienced this kind of policy when I use my cards at restaurants, supermarkets and department stores.

I would like the relevant authority to look into this matter and provide the consumers a place we can call for answers and report to if shops continue to wrongfully charge us.