It always starts with an innocent exchange of phone numbers. After all, the downstairs neighbor seems like a normal person, he offered, and it would be weird to turn him down. Well, it turns out you really should have turned him down because now you're getting incessant complaints about everything from noises to your dog. That's what happened to this Redditor , who started to receive a series of unhinged messages not long after exchanging numbers with her downstairs neighbor. First, it was a no…