Should I reply to "non-compete violation" letter myself or hire an attorney?

I was an employee of a software consulting firm A and was placed as a consultant on firm B for a few months. I was subsequently taken out of B and placed at another client C due to a better rate. After the assignment at C ended, I applied for a job in firm B and was accepted. I resigned from A and joined B.

B is not a software consulting firm. It is a manufacturing firm. The work I am doing at B is totally different from the work I did as a consultant at A. There is no non-compete agreement between A and B.

Now, my former employer A, has sent me a letter stating that I am in violation of the non-compete which was part of my employment agreement. They have asked for monetary compensation for damages.

The non-compete agreement that I signed is only applicable if I do something that is competitive with the services provided by A. To be specific, it would be only applicable if I join another consulting firm and am placed by that consulting firm at B, thereby depriving A of business. That is clearly not applicable in this case.

Now, the question I have is: should I reply to this letter myself or should I hire an attorney? Should I rather wait and see if A initiates any legal action before I hire an attorney? I am trying to minimize my expenses because the non-compete is clearly not applicable in this case.
I have already asked attorneys at B to reply to this letter. But they would be writing on behalf of B and not representing me.
What would it cost for an attorney to draft a response letter on my behalf?

thanks