Pranking Albus' spy system

You know that gag where you intentionally speak as if the reception from your phone is garbled and breaking up?

What if Harry or Hermione started doing that whenever they were within earshot of the many portraits in the castle? It would no doubt drive Albus up the wall with frustration, wondering if the enchantments were failing and leaving him bereft of whatever the teens were planning.

Writing-wise, I would imagine it be pretty close to how Hagrid or Fleur speaks with apostrophes in replace of certain letters.