SAMS makes changing telephone pre-fixes pretty easy (I don't say real easy, because you still have to enter all of the data). The nice thing is that you only have to enter the changes here - one time - and then all phone, fax and other phone numbers will change in all the modules.
Go to look-up codes
Change Tel Prefix Table
Open the window
Add new record
Enter Old Area Code
Enter Old Prefix
Enter New Area Code
Enter New Prefix (typically the same as the old prefix, but just in case).
Once all the new pre-fixes are entered, you are ready to run the program.
NOTE: Make sure everyone is out of the system when you run this program.
Go to Utilities
Change Tel Prefixes
It will ask you if you are sure you want to change prefixes. Say yes.