Pre-approval means nothing

I app**** for a pre-aproved loan on Clearscore. I was contacted by a salesperson who asked questions about my finances and I was honest and said during the interview that I do not think it is worth completing the application because I do not think I would qualify. She said that I should continue and I answered all her questions honestly. I got a call this morning confirming that the loan was approved they went so far as to confirm it on my banking app. Then I got a call from a very rude person going through my bank statements and asking questions I have already answered. He made me feel as if I was a chancer and afer everything my application was declined. This went on for hours. My entire day is messed up and I have achieved nothing.