I need to disable the auto-commit in the DB level for permanently.
PostgreSQL does not provide a knob to enable/disable this. If you don't use an explicit BEGIN your command will commit as soon as it successfully executes (and will rollback immediately if there is a failure). As Julien said, though, your driver may be doing stuff above and beyond the SQL commands you yourself send. Proper usage of you chosen driver/library is outside the scope of the general PostgreSQL mailing lists (and in any case this report does not constitute a bug report).
At least, unless you are using libpq directly or somehow manage to get this to happen in psql.