Thank you for visiting the Community space, Priyanka1.
If you have not activated the Multicurrency feature in QuickBooks Online, you can still change your home currency by following these steps:
Go to the Gear > Account and Settings.
On the left panel, click Advanced.
Scroll down to the Currency section,
From the Home currency drop-down list, select the currency you wish to change.
Hit Save, then Done.
As for the bank transaction entries that are already added, you'll want to undo them from the Categorised tab. Then, add them again with the correct currency from the For review tab in the Banking page.
Should you have more questions or need help with other task, please let me know in your reply below. I'll be right here to assist you. Take care and stay safe!