Any way to collect phone numbers when invoicing customers?

[suetyfiddle]

I make and sell one-off, high-value items. Because of this, I often book courier delivery for my products, which requires both my and my customer's phone number. Are there any settings I can use to ensure this is collected along with the address, when customers pay the invoice?

Thanks in advance

[ple-developer]

Did you find a solution to this by any chance? Having the same problem.