Check Part II SQL*Loader I can't remember when I last used it (being server side I use External Tables), but it should turn out something like
INFILE 'D:\ss\TT-Projects\Customer Apps\Client Dump\3GBundle.csv'
BADFILE 'D:\dd\TT-Projects\Customer Apps\Client Dump\3GBundle.bad'
DISCARDFILE 'D:\dd\TT-Projects\Customer Apps\Client Dump\3GBundle.dsc'
INSERT INTO TABLE tmp_mtnuga_3g_expiry_mig
fields terminated by ',' optionally enclosed by '"'
EXPIRY_DATE_T char "to_timestamp_tz(:EXPIRY_DATE_T,'yyyy-mm-dd hh24:mi:sstzh:tzm')",
STATUS_DATE_T char "to_timestamp_tz(:STATUS_DATE_T,'yyyy-mm-dd hh24:mi:sstzh:tzm')",
you must adjust the mask to match your data
If you changed from TIMESTAMP with TIME ZONE (which needs an explicit time zone) to TIMESTAMP WITH LOCAL TIME ZONE (which implies a time zone) then you should not have time zone pieces in your format mask.
You said your data is like "2013-08-31 17:14:56"
EXPIRY_DATE_T char "to_timestamp(:EXPIRY_DATE_T,'yyyy-mm-dd hh24:mi:ss')",
STATUS_DATE_T char "to_timestamp(:STATUS_DATE_T,'yyyy-mm-dd hh24:mi:ss')",
If you get an error again, post your current table definition, current loader file, and a few lines of data.
I am using 2 option to import into a table
Then perhaps you should use option #3 and download Oracle's free sql developer. It can import that data just fine.
The problem in TOAD will also have been time formats - you need to tell it the format to expect, and having the TIMESTAMP WITH TIME ZONE datatype will not have helped. SQLDeveloper also has its own storage of the formats to use.
At the database session level, and for SQLPlus, for TIMESTAMP WITH LOCAL TIME ZONE you'd need
alter session set nls_timestamp_format='yyyy-mm-dd hh24:mi:ss';
In TOAD this will be either a TIMESTAMP format or a TIMESTAMP WITH LOCAL TIME ZONE format.
I listed the options for SQLDeveloper and SQLPlus in https://forums.oracle.com/message/11177827#11177827