HUAWEI B525s-23a 4G/LTE WIFI ROUTER - Access via API

I am writing a PERL script to call the API on my router with some Curl commands. I want to send an SMS. So far I have managed to obtain tokens and login via the API (I am using sha256 and base64 to hash and encode the password into the correct format) but I cannot send an SMS. I keep getting error '100003' (Access denied). I have obtained the Session ID and Token from 'http://192.168.8.1/api/webserver/SesTokInfo'. Should I be using the same Session ID and Token as I logged in with or should I update them from 'SesTokInfo'?

Here is the section of code I am using:

my $message_data = "<request><Index>-1</Index><Phones><Phone>$PHONE_NUMBER</Phone></Phones><Sca></Sca><Content>hello</Content><Length>5</Length><Reserved>1</Reserved><Date>2020-02-17 02:00</Date></request>";

system "curl -v -X POST --data \"$message_data\" \"http://192.168.8.1/api/sms/send-sms\"
 -H \"Host: 192.168.8.1\"
 -H \"Cookie: SessionID=$SESSION_ID\"
 -H \"__RequestVerificationToken: $TOKEN\"
 -H \"X-Requested-With: XMLHttpRequest\"
 -H \"Content-Type: application/x-www-form-urlencoded; charset=UTF-8\"
 -H \"Accept: */*\"
 -H \"Accept-Language: en-GB,en;q=0.5\"
 -H \"Accept-Encoding: gzip, deflate\"
 -H \"Referer: http://192.168.8.1/html/smsinbox.html\"
 -H \"'X-Requested-With: XMLHttpRequest'\"
 -H \"Connection: keep-alive\"
 -H \"Origin: http://192.168.8.1\"
 --dump-header send_sms_session.txt";