My card keeps declining :(

I recently started banking with Nedbank and been having issues with my card, last week on the 29th of April I went to a Checkers store to do groceries and when swiping my card the transactions was declined, I called Nedbank to find out what the issue was and I was told that nothing is wrong with my card as I was worried that my card was blocked and I was assured that it was the merchant's fault and nothing wrong with the card. Today I went to Shoprite and used the card and again same story and decided to go to KFC to check if it was the merchant only to find that my card declined again. I cannot emphasize the embarrassment this puts me through and being looked at like I'm a ******** or trying to commit *****. I eventually used my original pin that came with the card and it worked however at the ATM the new pin works so I am confused and cannot go through this again, can Nedbank please sort this out for me ASAP.