Apple’s iPhone 4S went on sale on Friday, with an improved camera, dual core A5 chip and Siri. This year the iPhone was made available on three networks, adding on Sprint as the new carrier.

Demand for iPhone 4S is now being reflected by sales records for both AT&T and Sprint, who have reported that their one day record has been broken. AT&T reported earlier that they have almost doubled the number of iPhones activated in a day than ever before, causing servers to strain under the many new iPhone 4S activations.

As of 4:30 pm ET today, AT&T had already activated a record number of iPhones on our network – and is on-track to double our previous record for activations on a single day. These record volumes may produce slower activations for some customers, though our systems continue to run at record levels.

The original iPhone used to be exclusive to AT&T in 2007, but lost exclusivity when Apple joined forces with Verizon and now Sprint. Sprint has also reported that the iPhone 4S launch is the most activations and most units they’ve ever sold on launch day. Sprint reportedly broke this record by 1PM ET, making it the fastest sales day ever in Sprint’s smartphone sales.

Sprint product chief mentioned that it was the “best ever day of sales in retail, web and telesales for a device family in Sprint history.” He also mentioned that this is likely because of Sprint’s “truly unlimited plan”, with unlimited talk, text, and web.

This is the first time that Sprint has sold the iPhone, and it looks very promising. Apple’s choice of Sprint, and Sprint’s dedication to selling the iPhone 4S could turn out to be beneficial for both, Apple and Sprint.

{via Mac Rumors}