Skype, popularly known for its voice telephony services announced software for the BlackBerry and iPhone on 31st March, a week after the release of the beta version for Windows Mobile.

A few months ago, Nokia announced it would start shipping mobile phones with Skype pre-loaded. However, it's finding itself in trouble with iPhone users as they can only make Skype calls with Wi-Fi and not via their mobile phone.

This also reduces the wireless carriers revenue when an iPhone customer makes Skype calls with their mobile phone. Some mobile phone carriers such as T-Mobile are blocking Skype. "If the Skype programme didn't work properly, customers would make us responsible for it", said a spokesperson from T-Mobile.

Other carriers such as AT&T and O2 are allowing their iPhone customers to use Skype. They don't perceive it to be a threat because carriers provide data services only for moblie phones with customers having to pay around £21 per month for the voice service. But, some customers may opt for a plan where the majority of calls are free using Wi-Fi
Higher data spending will not offset voice revenue losses if the majority of users have an unlimited data plan for Mobile, Wi-Fi or both. In such cases, Mobile Skype may not prompt many data plan upgrades.