Approved Case, but Problem with Photos!

Hello

My name is Shad. I did applied for OPT in December 2015. They approved my case in February 2016. Then they sent me a letter that asked me to sign in a box that they provide within the letter and also asked me to send another pair of Photos.

So I did sent the letter with photos right after I received the letter. I signed with a pen that has a black ink as requirements, also took my pictures at Costco or Walgreen passport photo sections.

But Again in March I received the same letter, so I took pictures with more attention at a local Costco store, with all requirements I pulled up from USCIS website. But after a month, I received that letter again for the third time recently. Honestly, I have job offer, and I really need to start working! I also met an officer a local USCIS office and they submitted an inquiry which I never received an answer form them. I really need help and advises regarding my case and I need to know why they are keep sending me same letter and ask for photos and signature! Also I sen them by traceable mailing system, and they received my documents each time at California Office!

I need to know if there is anyway to contact an officer at California the office that sent me letters!

Thank you in advance and waiting to hear from you.

Bests,