These are top and recommended SMS Notification Extension For Magento Ecommerce
1) Landofcoder SMS Extension
SMS (Short Message Service) or simply “texting”, is a feature available with practically all mobile phones, allowing people to send and receive short notification messages

2) magecom sms extension
SMS have vital part in Ecommerce now days. People use and prefer more mobile services in order to carry together everything in a tiny smart phone. Ecommerce business owners also developing various services to make mobile friendly and provide fastest services to provide best user experience to their customers.
Link: https://magecomp.com/magento-2-sms-notification.html

3) Voodoosms SMS extension
Magento has rolled out the next generation of their hugely popular digital commerce platform: Magento 2.0. This heralds a new era of ecommerce, promising an engaging and personal shopping experience. With Voodoo SMS, you can now amplify this experience.
Link: https://www.voodoosms.com/sms-extensions-modules/magento2-sms.html