You can do so in 2 ways:
- Via UMB: Dial *500*99#
- Via SMS: Send an SMS to 9838 in the format REG Shalat30 / Sholat30 / Salat30 for 30-day subscription, REG Shalat15 / Sholat15 / Salat15 for 15-day subscription, and REG Shalat7 / Sholat7 / Salat7 for 7-day subscription.