Defective notice and return invalidated

In one of our case defective notice was issued stating that since the gross receipt exceeds 1cr you have not attached tax audit report but we won't agree with the same as our gross receipt was less than 1cr and we filed response to the same. The same defective notice was issued 6 to 7 times we have filed response in all but forget to file in last notice and therefore the return was invalidated. So my question is what can we do now. We have contacted to CPC but no response was received. Can we submit letter to Cbdt or can we file an appeal or anything else.