UCAS choices

Can I change my uni choices even after they’ve sent me an offer? I submitted my application on nov 26th, so it hasn’t passed the 14 day wait. I regret picking two “safe” unis that are offering me the same grade requirements anyway. Now I’m not seeing a point in having both offers. I don’t know what was wrong with me when I was picking my choices.

Would UCAS let me switch a uni or is it too late???