Call a UDF inside an Oracle Adpater message

I have an Oracle DB with a function that can be used inside an insert
statement

Such that

insert into CDI_SOR_DEFS (EX_SOR_NUM, SOR_REF, SOURCE_CODE,
CATALOGUE_SOURCE) values(DECODE(customer_card_loc(31,null,null),null,31 ,null),
'TEST','TEST','TEST')

(customer_card_loc() – is the function)

This works fine in SQLPlus however when i try and call this function
through Biztalk and an XML message

such that

<ns0:Insert
xmlns:ns0="http://schemas.microsoft.com/[OracleDb://LFC/CDI/Tables/CDI_SOR_DEFS]"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<ns0:Rows>
      <ns0:InsertRecord>
        <ns0:EX_SOR_NUM>DECODE(customer_card_loc(31,null,null ),null,31
,null)</ns0:EX_SOR_NUM>
        <ns0:SOR_REF>506003</ns0:SOR_REF>
        <ns0:SOURCE_CODE>W</ns0:SOURCE_CODE>
        <ns0:CATALOGUE_SOURCE>CATALOGUE</ns0:CATALOGUE_SOURCE>
       </ns0:InsertRecord>
</ns0:Rows>
</ns0:Insert>

It fails

Any pointers would be great

Thanks

Simon