System.ServiceModel (...) Invalid BillTo account Number for the user (Sameday) [Solution]

When processing Sameday orders you might run across the "System.ServiceModel.FaultException: System.Web.Services.Protocols.SoapException: Server was unable to process request. System.Exception: Invalid BillTo account Number for the user..." error:

This error happens when the BillTo account number is not added in the list of allowed accounts in the Sameday portal.

You can only use accounts added to the Bill field on the Sameday portal (https://sameday.dayrossgroup.com/Forms/CreateShipment.aspx?shipmenttype=NormalShipment&langid=en)

To solve this issue:

1- Verify Sameday portal, to see if the BillTo account number you intend to use is in the list of allowed accounts. On the Sameday portal you can only use the accounts from the drop-down below. You cannot enter any other account.

2- If the account is not there, reach Sameday support and request they add it, since nor the user nor techShip support is able to add it. Only Sameday and/or account owner is able to add permissions.

NOTE: We are not be able to change this because nor Sameday API neither their website allows it.