If the transaction is confirmed already then you cannot undone it. But otherwise I read some tricks that will make some adjustments while the transaction isn't confirmed yet. I found it in the first page of this this thread but I didn't verify since you need to do it accordingly.
the transaction has taken place then it cannot be canceled. like we pulled the trigger once pulled then it can't be canceled. be careful before making a transaction and don't rush into doing a transaction before we are sure of everything we do.