SMS bundle

[zakspeed]

I have a sim900 modem on arduino uno controller. On a door event I send a SMS to a cell number. This works correctly. The problem is that the credit come off the airtime balance and not from the SMS bundle. I used a prepaid vodacom simcard.
I need some help on this

 

[GreGorGy]

I assume the SMS goes to a normal number? Do you use AT commands to send SMS? Does the SMS send properly from the bundle in a normal phone