Do anyone know how a vendor can enter their phone number for bill pay if they live in Serbia?

Hello, @Shawn Millhouse.

Bill Pay integrates with QuickBooks Online Essentials, Plus, and Advanced. This fully integrated product lets you pay and track bills from your QuickBooks account and let you send payments international or domestic via ACH or check.

In adding the contact details of a vendor, it can only be done right away in your QuickBooks Online account. 

Here’s how:

1. Log in to your QuickBooks Online account and select the Expenses menu.
2. Under the Vendors tab, select the customer you want to add a phone number and click Edit on the upper right. 
3. In the Vendor Information window, fill in the contact information and click Save.

You can also use this handy article to get more information on how to wire payments to international vendors using Bill Pay: Send international payments using Bill Pay for QuickBooks Online. 

 Please don’t hesitate to leave a comment below if you need further assistance. I am always here to answer your QuickBooks related concerns. Keep safe.