Finally getting my refund! I wasn't hearing anything from iTunes Support, so I contacted them again yesterday, and got a response today. At first, the support person said they found my purchase, but that it was "free" and I was not charged -- but because I was deeply unsatisfied, they would give me a 5-song store credit on iTunes.
I explained to them that they might have seen one of my many attempts to delete and re-install the app, and reminded them that every download after the first one is marked "free" (you'd think they'd know that), and that I was indeed charged $2.99 plus tax -- even showing them a screenshot of my purchasing history with the original MobileChat download. I then said that while I appreciate the 5-song credit, and it's a much better value ($5) than getting my $3 back, I still wanted a
proper refund -- because I didn't want the MobileChat developers receiving a single dime from me.
So I got another response saying they'd credit my account for a full refund!
Slightly off-topic: I was quite surprised that the two e-mails I got from the support guy (his name was Adrian) was littered with grammatical errors. It's just odd getting any official correspondence from Apple and it sounds like a kid wrote it.