Really, the best way to deal with this is to remove all non-digit characters, then do whatever additional validation you may require, such as the number of digits or whether the number begins with a valid area code/country code, on what's left. That way it doesn't matter whether the number is entered as (assuming US numbers here) 987-654-3210, (987) 654-3210, 987 654 3210, 9876543210, 9 8 7-6.54321 0, or whatever else.
Concentrate on validating what's meaningful in the input (the digits) and not incidental details which really don't matter (how the digits are grouped or formatted).