I am enrolled in the company Defined Benefit pension program…

I am enrolled in the company Defined Benefit pension program for 30 years.
On August of 2011, I asked the company Human Resources for an estimated projection of my defined benefits monthly payments and the commuted value (lump sum) of the pension on my reterment.
I received this report on August of 2011, showing the monthly payment and the commuted value of the pension. At a company meeting on September of 2013, I was informed through a chance question that I no longer have the option of taking out the commuted lump sum but only the monthly payment option if I retired now, because I am now over 65 ( since last April). The company indicated that this according to the company submitted "plan document".
This information came as a total surprise and triggered a search by both the company HR and myself for some document where this stipulation was communicated to the employees. No communication was found by either the company or myself including the yearly statements going back many years sent out by the company . No other company employees knew about this. Incidentally, this stipulation was not mentioned in the report of Aug 2011 mentioned above.
I would still like to exercise the option of taking out the commuted value.

The question is "Is the company legally bound not to pay the commuted value or is it something that the company has control over?"
If the company is legally bound, but made a mistake in communication do I have any recourse or way to proceed?
Thanks,
George