Can anyone tell me if the answer to your secrect question can be changed at any time?

I have good reason to beleive that my main Yahoo! email accounts as been hacked into. The last time I was able to access it was July 31st. Apparently, the answer I give does not match what was set up - almost 10 years ago, and the answer conincides with the question, to the best of my knowledge, there isn't any other way that I would have answered the question. I have not had any luck when I phone support or with the emails going back and forth with "account-security". Any suggestions would be appreciated. If I was not the user of this account, would I go thought this much trouble to get back in? No, I'd find a way to hack into the account - which someone has done. I'm very frustrated at this point.