I have one of these 16 digit service cards from UB and I believe the change is because it is now a combined Laser and Maestro card.
Original UB Laser only cards had 19 digits, but Maestro follows the xxxx-xxxx-xxxx-xxxx credit card number style. This new card also has the 3 digit CCV code on the back, which I believe the original UB Laser cards didn't.
I haven't had any problems using the new card, but I notice in some chip and pin terminals I need to choose Laser or Maestro as the payment option before I can enter my pin.