Mod Note: The following is 100% incorrect and will get your Fiverr account BANNED.
You don’t have use to Fiverr.
You can use Paypal as well since it’s a widely known payment processor.
If you ultimately want to use Fiverr, then tell them on the phone that for both of you to have a safe transaction, they can pay through a well-respected freelance marketplace called Fiverr. Then send them an email with instructions and a link to your gig.
If they don’t know Fiverr, just request a payment from them using Paypal.
Mod Note: Posted edited, portions struck. It is a serious violation of the Fiverr Terms of Service to use any payment processor other than Fiverr. Do NOT follow this advice unless you do not care if your account is banned.