Editing transactions after the fact ?

[linux guy]

I've never used gnucash.

Provided that one has not "closed book" on an accounting period, can
one go back and edit past transactions ?

Lets say I paid a bill from a checking account and debited phone
expense.   Lets say I later found out it was supposed to be utility
expense.   Can I, after the fact, change the account on the
transaction from phone expense to utility expense ?  Does the posting
date on the transaction change ?

Thanks