I am trying to upgrade a MICS V5 to PRI The telco only allows me to use 4, 7, or 10-digits my 4 digits starts with 0 my 7th digit starts with 5. and the PRI will not allow me to use 10-digits. I am unable to use the 7-digits as my number starts with a "5" and for the life of me I can't find where in the system the digit "5" is used. Anyone please help