func (c *Call) FriendlyPrice() string {
	if c == nil {
		return ""
	}
	return price(c.PriceUnit, c.Price)
}
func (c *Call) FriendlyPrice() string {
	if c == nil {
		return ""
	}
	return price(c.PriceUnit, c.Price)
}
// FriendlyPrice flips the sign of the Price (which is usually reported from
// the API as a negative number) and adds an appropriate currency symbol in
// front of it. For example, a PriceUnit of "USD" and a Price of "-1.25" is
// reported as "$1.25".