Clients like me appreciate it a lot if a SMS is received from a service provider to inform me about the status of my job request. It is fast, the sms will reach the number it is sent to and you save money as a service provider by not calling the client.
Click this link,, and register for free. You will also receive free credits to try the service. I usualy buy 2500 sms credits at a time. These credits do not expire!