F1 2019 F1 2019 Rule Question....

[eyewants]

I am engaged in a full length 100%, no assist career. After making it to Q3, the last session of qualifying, don't I get to return the most worn tire(SuperSoft) and be able to start the race on a new set of supersoft, if I have it available to me in the pit? I am at the 5th race with 3 Q3 sessions and I keep getting stuck with the very worn super softs that I used in Q3 resulting in very early pitstops. Please offer some clarification, I thought this was something implemented for the year 2019.