Having 0% interest on your credit card is a good thing but you only get 0% interest on your credit card for maybe 6 months to the first year as an introductory offer.
After the time period passes then you have to pay some interest on the credit card when you use it because that's how the credit card companies make their money.
If the credit card companies never charged interest on the credit card when you used the credit card then they would make no profit on the money the credit card company lent to you.
So when you see a credit card offering 0% interest always read the fine print because it will usually let you know that the 0% interest is only for a certain time period and then after that you pay some interest on the credit card.