O2 has postponed the launch of its multimedia messaging service until mid-November.
It had planned to introduce this week but should still come in time for the Christmas market.
02 wants to sort out some problems in its systems.
MMS enables people to send photographs, cartoons and sounds from their mobile phone to other mobiles.
A range of camera phones is being launched at the same time as the MMS service.
These will allow users to take photographs with their mobiles.