Add this as built in code in the telephone formatting options so there are built in options to catch "bad" data, in this case incomplete phone numbers

US Phone Number Normalization
Goal: normalize to digits, then detect “short” values and exclude them.

Steps on the phone field

Telephone format (or use Replace to strip punctuation)
Normalize the phone first so only digits remain (remove spaces, dashes, parentheses, etc.). If you don’t use Telephone format, add Replace rules to remove “(”, “)”, “-”, “ ”, “+”, “.”, and “x/ext”.
Fixed Length Formatting
Fixed Length: 10
Append Value: choose a unique character, e.g., ~
Position: After
Result: valid 10‑digit numbers stay unchanged; any value shorter than 10 gets one or more “~” appended.
Replace (to exclude)
Incoming Value: Contains ~
Result: leave blank (set to nothing)
Notes

If you sometimes receive 11 digits with a leading “1” (US country code), add Shorten Data with Character limit 10 and “Remove characters from: Beginning of data” before step 2 to keep the last 10 digits.