Something like this should do the trick:
Let ( [
phoneNumber = Filter ( PhoneMobile; "0123456789" ) ;
phoneLength = Length ( phoneNumber )
Case ( Left ( phoneNumber; 1) = "0"; Right ( phoneNumber; (phoneLength -1)); phoneNumber)
) // Let
Okay, great! Thanks - where you've put 0123456789 - do I need to replace this as I want to apply to all the phone numbers in my table?
I took this from one of my solutions where I'm doing the same thing. I'm using the filter function just to make sure there are no spaces, + characters etc before I test for the leading zero. You can remove that if it's not required in your situation.
Simpler solution is to GetAsNumber ( FIleMaker Phone Record Field )
this will automatically drop the leading "0"
To get this working fully, I needed to use the following:
GetAsText (GetAsNumber (Mobile Number))
I needed to do this as when it's a number it formats really weird with a plus value for some reason.