BTM-2017 allows a phone number mask to specify the format of a phone number. If the phone number is not displayed correctly, use the following procedure to modify the settings:
Go to File > Preferences and Program Setup
Click on the Date Time Phone tab.
From the Local Telephone Format, select a mask that applies to your format. ("999\-999\-9999;0;_" is the most commonly used - in the USA).
If you do not see a format that works for you then design your own. Use the number 9 to indicate where a number goes, and for any non-numeric character in the format such as parentheses or hyphens, put a backslash in front of it.