Hello,

I don't know how your gateway works. You need to provide detailed version. What I can do now is to ask how can I explain the setting further so you can understand it better.

    'url' => 'http://example.com/api/sms.php?',
    'params' => [
      'send_to_name' => 'mobile',
      'msg_name' => 'message',
      'others' => [
        'param1key' => 'param1value',
        'param2key' => 'param2value',
        'param3key' => 'param3value',
        'param4key' => 'param4value',
        'param5key' => 'param5value',
      ]
    ]

Let me know what is no clear so that I can explain further. What I guess from your url is this.

URL = https://smsapi.greenline.lk/api/sendSMS/?
Send to name = number
Message name = message
param1key = key
param1value = theValueOfYourKeyHere

If you are not sure, you can check with your gateway team with above details.

Thank you