When we say "No"?

We received the following request. In fact, it was a claim:
"It’s funny how before we signed the contract all I was hearing was yes and now all I am hearing is no".

Here is our answer:
"All the technical details should be finalized and agreed upon during the initial discussions and signing of the contract, but not at the stage of performance. It is the „alpha and omega“ of professional software development. Statistics show, that 70% of software projects are not pursued to the end because of changes during development or implementation. To make changes at these stages is a sure way to kill a project.

We try to meet customer needs as much as we can. But consider two things:
Firstly, our product is a software product from a conveyor, not a software development service, and to make changes is not easy.
Secondly, to discuss each change several experts must be involved, who are not always easy to pull away from their current work.
Therefore, every such discussion is a headache.
We hope this explanation gives you an understanding that we are not swindlers".

Where we found the statistics - here are some old, but still valid surveys:
http://www.it-cortex.com/Stat_Failure_Rate.htm.

Once again, colleagues: second thoughts are best!