How To Export My iPhone Contacts As CSV
Whilst Apple does not support the export of the common excel file type (.csv) used by most services, there are ways around getting your contacts off the iPhone and synced with a service that is compatible with multiple platforms. Adding a contact to your iPhone will only save to your iPhone and can only be restored to another iPhone if you have iCloud activated or manually back them up. This makes it difficult for iPhone users to take their contacts with them if they wish to switch to another mobile device. But not impossible.
Export contacts from the iPhone as CSV
You can purchase this app for iPhone for $2.99 which will do the job: https://itunes.apple.com/ca/app/excelcontacts-lite-export/id385462419
You can also use paid Mac apps to export the Mac Address book contacts to CSV.
Export Address Book $3.99 by Stefan Keller - https://itunes.apple.com/ca/app/export-address-book/id402323447
Address Book to CSV $2 tp $4 By Fangcheng Yin - https://itunes.apple.com/ca/app/address-book-to-csv/id658182498
Note: You can avoid this problem by not using Apple services to manage your contacts, Thexyz Mobile Sync, G Suite and Microsoft Exchange will overcome the problems of being locked into Apple. There are also multiple third party apps and services.