Bulk SMS Production App getting 400 bad request using powershell

The "messages" is an array of object and the "to" number is also an array of phone numbers. Right now, only one phone number per "to" array as we don't support group message yet.

"messages": [
    {
      "to": ["+14155550100"],
      "text": "Hello Alice"
    },
    {
      "to": ["+12125550100"],
      "text": "Hello Bob"
    }
  ]

https://developers.ringcentral.com/guide/messaging/sms/high-volume/sending-highvolume-sms#http

I have figured out how to format the code, now Im getting a (503) Server Unavailable error. I am using the phone number that was provisioned for bulk SMS

 $AuthBodyTxt   = @{"from"     = "+14085555555";
                    "messages" = @(@{         
                                "text"     = "Hello Team testing";
                                "to" = @("+18315555555")
                                },
                                @{         
                                "text"     = "Hello Team testing";
                                "to" = @("+18315555555")
                                })
                    }

ConvertTo-Json -InputObject $AuthBodyTxt -Depth 3

{
    "messages":  [
                     {
                         "text":  "Hello Team testing",
                         "to":  [
                                    "+18315555555"
                                ]
                     },
                     {
                         "text":  "Hello Team testing",
                         "to":  [
                                    "+18315555555"
                                ]
                     }
                 ],
    "from":  "+14085555555"
}