After having released the CDMA version of the popular iPhone on Verizon Wireless last week, Apple - which has been selling the GSM version of the handset on AT&T thus far - has now published a support document that details the key differences between GSM and CDMA versions of the device.

The support document went thus: "iPhone supports many phone features, including call waiting, call forwarding, and conference calls. Depending on your wireless carrier's network technology (GSM or CDMA), there are different methods for enabling and using these features."

The chart that accompanied the support document showed that users of the GSM iPhone version can adjust call forwarding, call waiting, and caller ID settings in the 'settings' window; while the CDMA iPhone users have to dial numbers to enable or disable the features.

In addition, since the CDMA iPhone lacks a SIM card, a number of SIM card-related features are unavailable on this version.

Moreover, GSM supports conference calls of up to five people simultaneously; vis-à-vis CDMA iPhone's supports up to two calls simultaneously. However, while the CDMA iPhone boasts the ability to dial a hard pause; the GSM model lacks such a capability.

Meanwhile, even though Apple's support document reflects the company's intentions of heading off possible user confusion, AT&T's CEO Randall Stephenson has recently condemned Apple's App Store business model. At the Mobile World Congress in Barcelona, Spain, on Tuesday, Stephenson expressed his frustration with app stores that work on just one mobile operating system.