In case your Service No. have been automatic deduct bank account/credit card, so it allowed to make payment via website, If occur duplicate payments, the over payment will forward to paid in advance.
NT Contact Center 1888 (Everyday 24 hours)
NT eService Customer Support 0-2575-8172, 0-2575-7562 (Mon-Fri 8.30 a.m. - 4.30 p.m.)