Apple is working on new software for the iPhone 3G, which went on sale in Spain on June 11th, due to a number of complaints about calls being prematurely terminated.
The problem of calls being cut off half way is apparently due to local or environmental interference and Apple is busy trying to produce new software which can be downloaded onto the phone to resolve the issue.
The iPhone originally went on sale in the USA on June 27th 2007 and proved very popular. The current version, the iPhone 3G, allows for fast internet access and went on sale in Spain on June 11th 2008. It is currently only available through Telefonica and Movistar