global void sendsms()
    {
        String username = 'JRjNX4xr0yQDTndP9vfa' ;
        String password = 'vyAK$ja7NhLOcI8pX34lokMxUue0RZ.i';
        String message= 'Hi this msg. is for testing of "sending msg.on mobile when SLA breach"';
         HttpRequest req = new HttpRequest();
        req.setEndpoint('https://api.us1.corvisa.io/sms/send');
        req.setMethod('POST');
        String phonenumber='+15123355101';
        //String body='{"text":"  '+message+'","to_number":"'+phoneNumber+'"}';
        //String body='{"text": "Test Message","to_number": "+15123355101"}';
        //String body='{"messages"":""Hi this is for test","to_number"":" "+15123355101"}';
        String body='{"messages": [{"text":  "text of message","to_number": "+15123355101"}]}';
        Blob headerValue = Blob.valueOf(username + ':' + password);
        String authorizationHeader = 'Basic ' +  EncodingUtil.base64Encode(headerValue);
             req.setHeader('Authorization', authorizationHeader);
             req.setHeader('Content-Type','application/json');
             HTTPResponse res= new HTTPResponse();
             req.setBody(body);
             Http http = new Http();
             //res.setStatusCode(200);
             res = http.send(req);
             system.debug(res.toString());
    }