Service code &1 not defined for small parcel carrier &2

What causes this issue?

There is no <DS:DE.XSISRVC>service code</> defined for the
<DS:DE.XSITD>small parcel carrier</>.

System Response

The value cannot be posted.

How to fix this error?

Choose a valid service code or create the service code you need for the
small parcel carrier in the <DS:TRAN.VTRC>Cockpit</>.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.