Block feature won’t work on my IPhone 8 Plus 12.1.1

My IPhones block feature doesn’t work. When I go to block someone i still receive their texts. I’ve tried everything from going to settings> messages>blocked> add new, to resetting my network settings, shutting it down, and updating to the newest version of IOS. There’s a number I need to block to stop receiving their messages asap. Please help!!