Hello. Welcome to JustAnswer, a paid global support site.
For clarification, we are not Google. Google does not provide any type of live phone/chat support.
It is very likely that you account has been compromised either through a low complexity password XXXXX a successful phishing attempt.
I understand the methods you have taken to recover your account. I want to make sure that all avenues are covered. If you have exhausted these options, it is highly unlikely you will ever recover your account.
First you must be willing to accept that you may never recover your account.
Please go to the forgot my password page (https://www.google.com/accounts/ForgotPasswd).
If that option doesn't work, you can trying the cannot access my account page (https://www.google.com/support/accounts/bin/request.py?ara=1&hl=en&contact_type=ara&ctx=ara)
If you can get through and change your password, I would suggest using a password XXXXX at least 10-20 characters, with a mixture of UPPERCASE, lowercase, and numbers (1234), preferably alternating (i.e. M1y2p3A4s5S6w7O8r9D). Also make your security questions very difficult to answer. Don't use something as common as mother's maiden name or first child's name. Make the answer very difficult, and I would even suggest throwing in a sequence of numbers at the end of the answer to make it harder for the hacker.
Also, before you log in, look at the address bar of your browser to make sure you are on the right site to log in. (i.e. make sure your address bar says https://www.google.com and not something like http:// 123abc. randomurl.com/ www.google.com/). A lot of phishers/hackers have been using the tactic of making a page look exactly like your log on page to trick you into typing your password.
If in doubt, type in the base URL yourself (i.e. http://www.google.com) in the browser.
If you still cannot get through or the hacker has modified your security questions/answers, and you have no credit card information or billing information on record, you have no way to verify your account, thus this is nothing you can do.
Unfortunately, Google's live support is almost non-existent.
The problem with free e-mail services is that they rely on security question/answer combinations for verification. If you forget these and/or your account is hacked and a hacker changes the info, you have no way to verify your account. With paid e-mail services, you can easily verify your identity by verifying your billing information.
In the future, my suggestion would be to invest in a paid email account service so that you can always verify your billing information in case something like this happens.
If you have used the methods above and you have been unsuccessful in recovering the account, there is nothing you can do to recover the account.
Let me know if you have any questions or comments by replying to this thread. I am here to assist you! Good luck.