It's incredibly unlikely.
There are very occasional stories of people getting in on results day, but they are far more likely to be: -
1) People who missed their offer but universities decided to take them anyway.
2) People who were on a waiting list and who achieved AAA or better
3) People who got fantastic A-level grades and got very VERY lucky phoning up on the day.
Given how many people get AAA and do not get into medicine, calling around on results day with AAB is really unlikely to succeed. Not saying you can't give it a shot, but I wouldn't get your hopes up.