Sephardic, and Ashkenaz Jews-

Sephard literally means Spain. Most Sephardim follow the rulings of Maran Shulhan Aruch. Sephardim usually follow the basic "din", while the Ashkenazim usually follow the stricter "Halacha". No matter which you follow you are Jewish, and you are correct. One may not be lenient if they follow the stricter Halakha. The only way to change Nusach, is through Hatarat Nedarim-Releasing your vows, with a Beit Din.