IPhone 4S still says 3G even when connected to home wifi?

So I'm sitting at home, phone is connected to my home wifi. Internet is loading totally fine but my phone still says 3G instead of the wifi icon. I'm only pay as you go which doesn't include 3G, so it couldn't possibly be running on 3G cause I have no money in my phone. I disabled 3G on my phone anyway, and the icon changed to a circle, still no wifi symbol but Internet is still loading fine and at normal speed. What's wrong with my phone?
It also does this even if I connect to other wifi spots outside of the house.

Well problem #1 its an iPhone. My android has 4gs all the time just sayin

That is weird. Is your iPhone jailbroken?

Try holding the Home and Power buttons to force a hard reset (wait till the Apple logo comes up). That sometimes helps with odd/intermittent faults.