While we can't find the exact information about the code "UT03ML", calls to a disconnected or non-working number would be diverted to an intercept operator.
Intercept messages is left to the discretion of each local telephone company. The code might be used as a standard intercept message for a disconnected cell phone.
Just like when there's a network problem. They are using codes (standard codes for network problems) after an intercept message so network engineers could identify where the call is terminating with an error.
Some network provider adds the new phone number after the intercept message. However there are cases that an error occur on the network providers end when the disconnect order was placed. This may also be the cause of an "error code" at the end of an intercept message, instead of having the new phone number.
Tracking down someone's cell phone number can be difficult, if not impossible. After all, one of the reasons that people purchase a mobile phone is so they can have some measure of anonymity.
However, that doesn't mean that finding a cell phone number listing is an impossible task. Check out some tips on how to find a cell phone number online at About.com.