libphonenumber

https://github.com/google/libphonenumber

檢查電話號碼格式是否正確 還會顯示分類:FIXED_LINE、MOBILE、VOIP(070門號)、TOLL_FREE(080門號) 

DEMO: 
https://libphonenumber.appspot.com

ref:
https://www.twilio.com/blog/validating-phone-numbers-effectively-with-c-and-the-net-frameworks

https://medium.com/frochu/libphonenumber-example-app-f60680faa599