A developer recently stumbled upon something that proves that the 4G iPhone is already exists and that Apple is probably testing the device.
Cydia developer Krishna Sagar recently discovered code strings in iOS 5.1 that contained the text: "Enabling 4G will end your phone call. Are you sure you want to enable 4G?"
It also contained various other mentions of enabling 4G on the phone for calls and FaceTime.
"While most references to 4G in the strings could be for the iPad, references to calling features is pretty solid evidence that Apple is at the very least testing a LTE iPhone," wrote 9to5Mac.
AT&T did begin calling its HSPA+ service on the iPhone 4S 4G, but switching between that and 3G would not end a phone call or a FaceTime chat.
The new iPhone is rumored to feature a 4.6-inch retina display and will launch sometime in the second quarter of this year, according to South Korean media outlet The Maeli Business Newspaper.
It reported that Apple has decided to go with a bigger 4.6-inch display for the next generation iPhone and has already begun placing orders to its suppliers.
Both LG and Samsung, who normally make the screens for Apple's mobile devices such as the iPad and iPhone, declined to comment on the news.
Samsung normally uses OLED displays in its Galaxy devices such as the Tab, S2 and Nexus. The high-definition Retina displays made for the iPad contain several times as many pixels within the same area.
The iPhone 4S that was released last October went on to be the world's best selling smartphone. Apple was expected to unveil the iPhone 5 last year that was rumored to feature a larger display. However, the company ended up releasing the 4S that features the exact same design of the iPhone 4.