why is my cell phone playing up?

I have a cheap Samsung TXT, which is basically an update of the Gravity 2 I had for a couple of years previously, and I had no problems at all with the Gravity 2 (until it went through the washer in my pants pocket).
The TXT is only a few months old, but has begun to do strange things. It temporarily freezes on occasion. My contact list magically begins to reproduce entires on its own - for example, this past weekend I found that each entry suddenly became 5 or 6 identical entries EACH. Occasionally when I try to access my contact list, it will not allow me to, telling me that "contact backup sync in progress - end sync? (yes or no). I don't even know what the heck that is, and dont even know how to initiate such a process. Sometimes when I try to charge the phone, it tells me "CHARGING PAUSED, WRONG BATTERY INSTALLED". I have to unplug and replug the charger, remove and replace the battery multiple times before it will finally begin to accept the charge - the battery is the original Samsung battery that came with the phone.
I don't know much about cell phones, but does this sound like a problem with the battery or the phone or is it even possible to tell from these symptoms?
I don't want to go waste money on a new battery if the battery isnt the problem, because I cannot return a battery for a refund.
Anyone have any ideas? If more information is needed I can gladly supply it.
Thanks!