Flipkart — Flipkart not able to change my registered mobile number

I am not able to change my flipkart plus account registered mobile number as it says the "identifier is already in use".

I had 2 flipkart accounts. I deactivated one normal account with the number 6282*.

Then I have one flipkart plus account with no number(only email id). When I tried to add my number 6282* to this plus account it is showing "identifier is already in use".

I want 6282* as my flipkart registered mobile number please help!!!