Substantial cash transaction

We are HUF and have pan card in name of HUF and current account in the name of HUF.
Banks have taken my pancard and my sons pan card for purpose of Authorized Signatory / KARTA and mapped to the HUF current account.
Now if i login to my and my sons income tax online its showing

"with Substantial Cash Transaction" in individual accounts as it was mapped to HUF current account.
Plz help me what to reply for this response.
Can i reply that Transaction in the account are considered in return of other account ?

Plz tell me the exact words to reply as i am poor in english