Unfortunately, most Charismatics are not very well-trained. They almost believe that it is wrong to study the Bible, and to understand it doctrinally by the Greek text. While some would deny this, in practice that is often how they operate when it comes to proving its message from the Greek language. I have seen them even get angry if you say, "The Greek text says …" They seem to believe that the KJV was inspired and is our actual Bible. They cannot get it through their heads that our English versions are just that, versions! But the proof that in both Acts and 1 Corinthians, we can demonstrate that tongues in both cases was a language and not some aesthetic mumbling.
In Acts 2 4 it is written that when the Spirit fell on those standing about "they spoke with other tongues. In Greek this is heterais glossais. In 1 Corinthians 14:21 (quoting Isaiah 28:11) Paul puts the two words together and writes the same thing with: hetroglossois. The meaning is identical and is translated other languages.

If I were a detective and went to the robbery scene, and found the same finger print in the bathroom, and in the den, I would rightly conclude that the finger prints were left by the same person. If I have the same phrase describing this miracle of languages in two different places, I would assume I am looking at the same phenomena. A language is thus in both places!

But this is too complicated for many Charismatics to understand. It is as if their biblical reasoning cannot go that far! But the fact is that they want to believe what they want to believe, when they want to believe it, never mind what the Bible says. And by the way, I have had Charismatics say just that. "But I don't care what the Bible says, my experience comes before the biblical text!"

I hope this helps.
Dr. Mal Couch