Samsung :: Flight: Stores Txt Messages To Sim Card Rather Then Phone Memory / Changable

I am absolutely in love with this phone except for these three issues. First, I am constantly texting (the reason I got this phone. Sent messages are stored to the phone without any problem. However, all incoming messages are stored to the sim card. I can probably take 30 messages before it fills up completely.This gets annoying because I am constantly having to delete my inbox when I rather not be doing it.I checked all over the phone for some sort of option to change this but have had no luck.Any one know if it is possible?
Another problem is that I plug the phone in every night to charge.When I wake up, it is fully charged. However, when I unplug it, it flashes "Low Battery" and powers down.I can turn it back on and the battery is full but this gets pretty annoying.Any hear of this before?Finally, is there any way to change the images that show up on the locked screen?They are nice but are annoying after some time.