Mismatch of name in pan and income tax records

My clients name as per PAN is ABC and name as per income tax records is BAC. the first name and middle name is shuffled. no change is made by client himself. till now the names were matching. while filing tax return came to know that name is changed in income tax site or records. the client is clueless how this happened. there's no option to edit name in income tax website.
The name as per PAN is correct and same as aadhar card.
pls advice how i can rectify name as per income tax records.