How do you teach your first nintendog to remember his name?

I have already past the part where he learns his name for the first time. But it says "keep saying your his name so he can get use to hearing it" so i call him until he comes up to me i pet him on the head and click back and I keep doing this until a message says "It seems dexter has forgotten his name" I'm so confused i have the game chiwawa and freinds and its a restarted game. Im owrryed that restarting it could be the reason its impossible for my dog to learn his name.Should i be petting him in a certain place for a certain time? Should I be on the dog status screen when i cal him?