Help LG Optimus One P500 2.3.3 Heating?

[abcindy]

I bought LG P500 2.3.3, i noticed it started heating (after 15-30 mins of texting), i went to the customer service and they just reset it, then nothing happened. It heated again, I came back the other day, they changed the battery. then after 3 days it started heating again. I came back and they resoftware it in 2.3.3 again and downgraded the software version from v20g to V20d, then nothing has changed! is heating normal to this phone or it is defective?