Listed here below in random order are some providers:

Always Active Technologies
BulkSMS
Clickatell
Grapevine Interactive
Innotel
Marketel
My Message
Panacea Mobile
Shark SMS
SMSPortal
Telfree
Note that this is not an exhaustive list. If you know of any others which you would like to have added to this list, then please email engage@siliconcape.com with a link to this page and the required info