Do you charge for sms feature ?
"Yes there is a nominal charge for sms. Because it is provided by third pary."
Sms charges are post paid or prepaid ?
"Admin can buy sms as prepaid. Charges differ for the number of sms they buy upfront. When you buy more sms you get more discount."
Is there any expiry date for sms ?
"There is no expiry date for sms. It ends only when you close your account. But once sms is purchased there is no refund."