I think we need to clarify a few things:
1. You're posting in the LG Optimus G forum--is that the phone you have? I'm not aware of the Optimus G being a pay-as-you go phone.
2. The specs for the Optimus G show it has 2 GB of system RAM and 32 GB of internal storage ROM, which doesn't seem to fit what you're describing.
3. We need to make sure we're correctly distinguishing RAM from ROM. The system RAM is where open apps reside--Android likes to keep apps open in RAM to allow for quick and efficient app opening and switching. Apart from the apps you open on your own, you don't necessarily have control over what other apps are open, because the system does it intelligently, depending on usage patterns and a particular app's code. The more RAM you have, the faster and more efficiently apps will run. The Android OS will generally try to keep RAM anywhere from 75-90% full, but sometimes things don't work quite right, and the RAM gets too full, which can potentially bog down the system. Phones come with anywhere between 512 MB and 2 GB of RAM--512 MB is pretty minimal these days for what Android needs. You can see how much RAM you have and how much is in use in
Settings>Apps>Running, along the bottom of the screen.
4. Internal Storage ROM is where you install apps, and where those apps store data (e.g., text messages, photos, etc.). Typically, the lowest amount of ROM a phone comes with is 4 GB, but 2-3 GB of that is taken up by the OS, so there's usually only about 1 GB of usable storage memory. The way Android apps are these days, that 1 GB can get used up quickly after only installing a few apps, and having those apps build up data. You can see how much total internal storage memory you have and how much is being used in
Settings>Storage.
For more info on this, see my guide here:
http://forums.androidcentral.com/am...roid-memory-how-deal-low-memory-warnings.html