Clearscore advise not so lekker

So when I check my credit score after paying off my debt, Clearscore advises that to improve it you need to apply for credit...either a store card or credit card. I tried applying for a credit card through Standard Bank and was declined because they claim I have a credit card with them which is not true. Now I have what they call a 'hard inquiry' on my profile which will stay there for a year and does not look good. So what kind of advise is that?