Prevent the Account Auto fill from Contact while creating Activity in Siebel

I am trying to stop the Account Auto fill from Contact while creating Activity in Siebel.

Requirement

(1) Create an account record

(2) Create an contact record with associating the account created in the step(1).

(3) Create an activity record and associate the contact created in the step(2), you will see that the account record created in the step(1) is automatically associated to the activity.

(4) Requirement is to stop auto association of Account to Activity

I have tried the steps mentioned in the article

(Doc ID 1901540.1) but the steps did not help achieve the requirement.

Kindly help