A toll-free phone number for your Shopify store gives you credibility and signals your customers you’re serious.

From the Krebs on Security blog

Scammers are using invoices sent through PayPal.com to trick recipients into calling a number to dispute a pending charge. The missives – which come from Paypal.com and include a link at Paypal.com that displays an invoice for the supposed transaction – state that the user’s account is about to be charged hundreds of dollars. Recipients who call the supplied toll-free number to contest the transaction are soon asked to download software that lets the scammers assume remote control over their computer.