Visa stamped for 3 months when the i797 is valid for next 2 yrs

I have my i797 valid till sep 2018 however, when I went for the stamping last month, I got my H1B stamped only till Nov 2016. As the H1B is valid only till November, I got my i-94 stamped till Nov 2016 and the CBE officer said that my petition has been backdated later in Jan 2016 from Sep 2018 to Nov 2016.

My attorney was surprised with this scenario and suggesting to apply for a H1 extension. Can anyone help me with a better option than this…

If the petition has been backdated to Nov 2016, then extension is the only option.