ISDN Type of Number (TON)

US TON have three types
Subscriber
- 7-digit subscriber number
  - 3-digit exchange code
  - 4-digit station code
National
- 10 digit number
  - 3-digit area code
  - 7-digit subscriber number
International
- Variable length (11 digits for U.S. numbers)
- Country Code (1 digit for U.S. country code 1)
- Area Code (3 digits for U.S. area code)
- Subscriber number (7 digits for U.S. subscriber number)
Based on the TON, perform different ANI transformation