Do you have Aadhaar Card? Is your name "Thumatla" in Aadhaar Card? Have you any proof for correction. If your birth is registered in Mpl/Corpn/Panchayats, then yourself and your parents shall file affidavit notarized, proofs if any and application for correction of surname. Otherwise file an applicaton at govt. printing press Gazette department and obtain the name correcton certificate.