This service has solved many of my problems and I am completely satisfied with it. I would like to say that I have not little experience with other similar services, but I think this is one of the best.
Good software for sending SMS to clients. As for the price it's quite cheep in compare with other companies.
Jasmin SMS Gateway - Jasmin is a very complete open source SMS Gateway with many enterprise-class features such as:
Octopush - Octopush is a company providing technology-based communication solutions, including SMS, Web solutions, and Email APIs.
KAPSYSTEM - KAP Computer Solutions Pvt. Ltd.,
E-goi - Email Marketing companies, SMS Marketing, software email marketing.
Textmagic - The all-in-one solution for all your business texting needs - marketing campaigns, two-way SMS chats, reminders, notifications, and internal staff communication.
CheapGlobalSMS - Send instant bulk SMS worldwide, with reliable SMS delivery and reports in real-time.