credit card used one of my relative with my permission for one year

My turnover is 10 lakhs and I filed my return with income 10 lakhs

actually my relative used my credit card and he used for one year and total credits in credit statement is 30 lakhs

Now I received a assement order that
your total credits are 30 lakhs and you have shown only 10 lakhs in income tax return and balance is undisclosed income so pay tax for 20 lakhs

with my relative I went to Assessing officer and my relative changed the words that I don't know I have not used the credit card

so pls give is there any case laws in favor of me