Key &1 is not permitted for this type of transfer

What causes this issue?

You can only enter the following values as a key for the type of
transfer:
1 Telegraphic transfer (T.T.)
2 Mail transfer (M.T.)
3 Check
The key for the type of transfer is stored in <DS:DE.DTAT16>instruction
field 1</> for the data medium exchange.

System Response

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

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.