Unable to upgrade OS

Please help me out with this.

I have a macbook pro (mid 2012), and the current OS version it has is OS X 10.8.5 I missed the regular updates. But now I am not able to use it. So wanted to upgrade to latest compatible OS.

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I tried checking for the latest update in App store but on clicking the get OS option I get an error pop out having message "Product distribution file could not be verified".

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Also I tried using the boot time commands

option+command+R

shift+option+command+R

command+R

each of these seperately....each time.. but still it took me to the same OS X 10.8 (mountain lion)

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What should I do now...?? Is there any other option available. How about service centres..?