Does 4g work on an iphone 4s with simple mobile?

The phone works, barely, and the best it ever does 3g. Can i fix this?

The phone will work great on 4g provided your carrier is supplying the signal & your battery is in good working order. It's awesome!

The phone will work great on 4g provided your carrier is supplying the signal & your battery is in good working order. It's awesome!