SMS gateway and API

General information for the business: SMS/Text Marketing Software
Description of requirements/functionality: I would like to have my own system to run customer's text marketing campaigns.

http://www.innovativetxt.com/
https://www.my-cool-sms.com/
http://www.twilio.com/sms/api
http://www.exetel.com.au/oldweb/corporate-sms.php
http://www.txtimpact.com/sms-gateway-api/

you may take a look at given references, i actually don't wanna pay them against each text but would love to have my own system and API for resell.

Please feel free to ask me if you have any questions or concerns.
OS requirements: Windows
Extra notes: just would like to have my own panel where i can manage the Text Marketing Campaigns of my customers and also would able to sell that service to anyone like the mentioned URL's does.