My case: Day 1, with 3 days prepaid net. (100 php prepaid)

It changes from WCDMA SUN then to HSDPA SUN.
In some occasions, it turns to EDGE SUN (This one seems like a state of NOT having a net, without disconnecting. But when reconnecting, its as if your times up with prepaid or no net at all...) and there's no way I can 'change' this even though I get to think it's the USB's/laptop heating that causes it, there's no change until I have not use the USB for sometime (Which ranges from a minute to 5 hours).
1st thing is can someone explain the acronyms? I don't have knowledge about networking. My searches doesn't specify about all the sudden changing.
2nd question is; why it changes? I'm not asking why the net speed just all sudden from 1.5mbps goes to 0kbps.
The main issue is why it changes acronyms... And I'm mainly pointing it why it turns at EDGE SUN by random.

I tried searching what this is, though it doesn't answer why it changes and what's the relevance. (Or a way of explaining it in search engines. And I don't get the technical terms...)