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Someone needs customer cell phone numbers in files.
Google spreadsheet is good file for saving cell phone numbers.
If you use spreadsheet, you can send your data to cell phone using Zapier.
(must join google and zapier, and sync contacts with your phone)
Step1. input phone numbers
Step2. Create zap "Create Google Contacts from new Google Sheets rows"
Step3. Edit zap - GS
Step4. Edit zap - Contacts
Maybe you confused correct fields.
Step5. Check your contacts
If you are lucky person, you will success first time.
Step6. See your phone
Interval 15min, Zapier sync google contacts.
Good Luck.
Need more Zapier or explains are google search results.