Some of you may have already noticed you get an SMS box on the left column of your gmail account recently. This turned out a lot more handy than I first thought. You can pick any Wataniya or Zain phone number to SMS for free. When the person replies from his device however they are charged the standard SMS price usually 15-25fils per SMS.
The way this works is you get 50 free SMS messages. When the person your contacting replies you get 5 more SMS messages but your maximum limit is 50. So for example if I send a message from Gmail and have 30 messages remaining I will get 5 More SMS messages once I get a reply making me have 35 messages remaining. If you reach zero, it will shift to one 24 hours later.