Q: serial no. says product has been replaced

i was supposed to contact apple support since im having problem with my iphone6s so before i could contact them i need to put my serial no. to my surprise my serial no. says that "Our records indicate that this product has been replaced. Please provide the serial number for your replacement product to find the support and warranty coverage information. For more information, please". 

i havent send my iphone for replacement yet and was still planning to do it since my phone alwats hang/crash few days after i updated the ios. And sometimes i have to restore my phone through itunes  because i cant update it. and i just recently restored my phone because it crashed again for two days and just showing the apple logo.