docs: add note about Pickup Contact Person

README.md

@@ -23,7 +23,10 @@ bench --site $MY_SITE install-app erpnext_shipping
 ```
 
 ## Setup
-For the compare shipping rates feature to work as expected, you need to generate an API key from your service provider. Service providers have their own specific doctypes similar to those from the `Integrations`. They can be enabled or disabled depending on your needs.
+
+Some shipping providers require the contact details of the pickup contact. Please make sure that the **User** selected as the _Pickup Contact Person_ has a first name, last name, email address, and phone number before submitting the **Shipment**.
+
+For the 'compare shipping rates' feature to work as expected, you need to generate an API key from your service provider. Service providers have their own specific doctypes similar to those from the `Integrations`. They can be enabled or disabled depending on your needs.
 
 ![LetMeShip 2020-08-05 09-54-28](https://user-images.githubusercontent.com/17470909/89377411-500c4f80-d724-11ea-8fe5-b11fec2a5c27.png)