If the dots are in your csv data, then you are good to go.
If you have mixed formats with (), dashes, spaces, etc, then you might need to remove all of that and then apply the periods in the right positions. Essentially, clean the value into 10 digits, and then take the first 3 digits, add a period, three more digits, then another period, and the final 4 digits.
The cleanest way to do this is to add a Variable in InDesign with a bunch of FindAndReplace() nested together to clean it up: (If you have other extra characters in the data, then you need to strip that out as well. Extensions will not work with this approach, nor country codes)
FindAndReplace(FindAndReplace(FindAndReplace(FindAndReplace(FindAndReplace(|->[Phone], "(", ""), ")", ""), "-", ""), ".", ""), " ", "")
Then we bring this into the ADOR:
SubString(@{PhoneJustDigits}, 0, 3) & "." & SubString(@{PhoneJustDigits}, 3, 3) & "." & SubString(@{PhoneJustDigits}, 6, 4)
I've attached a sample InDesign file and a simple csv.