@HeiroftheSeas given that I have them at the camps in America for most of the summer, do you really think that Dobby could pop into the camp without being noticed? Not to mention that the barriers around the camp keep out everything that is not a demigod, god, or satyr. Someone would have to allow Dobby in, but no one knows who Dobby is at this point. As for stealing post, the Weasleys can't afford to send stuff across the Atlantic. I don't know if Hermione would have a phone with international coverage, so Harry would likely call her, as he did get a phone from Leo. They can teach Ron how to use a phone correctly, so that would lead to almost no post for Dobby to steal. Until they get home from America, and Errol can fly to them without dying of exhaustion.
