The most effective method to transfer CSV contacts from a PC to an iPhone is by converting the CSV file into vCard (VCF) as iPhones support VCF natively. One option to consider is Softaken CSV to vCard Converter, which gets the job done without connecting to the Internet on a Windows system, and no data loss, as it keeps all the contact details such as names, phone numbers, email addresses, birthdays, and notes. Once you have the VCF file, you can just email it to yourself or import it directly into your iPhone using iCloud/Apple Contacts. Softaken also has a free demo version of the application, so you can test it before purchasing.