How much does a phone call alert cost?
On-call schedules and escalation policies are free. A phone number is billed like any other alert medium, with the same monthly price per medium.
Each call uses 2 SMS credits, taken from your prepaid SMS credits. Without enough credits, the call is not placed and you receive an email inviting you to buy credits.
If no carrier accepts the call, the credits are refunded. A call that rings but is not answered is charged, since it was placed.