I have seen your requirement for the SMS plugin. I can suggest you a Magento 2 SMS Notification Extension. It will help you to send an SMS to your customer. Also, we will help you to integrate with 3rd party platforms like msg91 and pinpoint.
The Feature Of This Extension Is as Follows:
Any SMS Gateway API Supported sending different order notifications.
Option to set a custom message for different store events
Send Dynamic notifications using Dynamic variable fields
Admin can add a mobile number to get notified of each store's updates
OTP at Registration and OTP Before Checkout Feature
New Feature for Cancel Order SMS
Easy to use Shipment tracking variables in the shipping notification