Trying to send SMS to OVMS Hologram sim

I have been trying to send a sms to my car to no avail. This is my PHP code:

<?php $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, ""); curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE); curl_setopt($ch, CURLOPT_HEADER, FALSE); curl_setopt($ch, CURLOPT_POST, TRUE); $requestObj = [ 'apikey' => '672kBamrf5H5ihcZIxNIj4********', 'deviceids' => ['2916755'], 'deviceid' => '2916755', 'fromnumber' => '31613357731', 'body' => 'lock 0000' ]; $requestStr = json_encode($requestObj); echo $requestStr; curl_setopt($ch, CURLOPT_POSTFIELDS, $requestStr); curl_setopt($ch, CURLOPT_HTTPHEADER, array( "Content-Type: application/json" )); $response = curl_exec($ch); curl_close($ch); echo var_dump($response); echo $response; ?>

This is largely based on the documentation and some tips on this forum. It does not work. Any help would be very welcome.