I receive a text message of a missed call. That text message contains the callers number, and suggests 'press the call button to return call'. HOWEVER.. The callers number is displayed as 44 (xxxx xxxxxx) (without the brackets, and numbers replacing the x's).
The PROBLEM is the contained country code (44) is seen as invalid as it SHOULD be +44. Therefore your (3's) system is displaying the country code INCORRECTLY which then fails when one taps the 'call' button. Maybe your techs can address this issue?