Canceling a User's Subscription with an API Call

I am having been following the API guide at https://www.zoho.com/campaigns/help/api/contact-unsubscribe.html

and have difficulty understanding what is going wrong with my implementation. I am testing the call on a local server (Rails backend) and am getting the following response error (listkey and authtoken are removed from this example):

ZOHO_CAMPAIGNS = Faraday.new("https://campaigns.zoho.com/api/xml/",

params: {

authtoken: AppConfig.zoho.api_key,

scope: "CampaignsAPI",

# listkey is for the "test test" mailing list

listkey: "-----"

}

)

def unsubscribe_user(user)

remove_subscription = ZOHO_CAMPAIGNS.post do |req|

req.url "listunsubscribe"

req.params["contactinfo"] = "<xml><fl val='First Name'>#{user.first_name}</fl><fl val='Last Name'>#{user.last_name}</fl><fl val='Contact Email'>#{user.email}</fl></xml>"

end.body

xml = Nokogiri::XML remove_subscription

xml.search("FL[val='Id']").text

end

Request:

#<struct Faraday::Request method=:post, path="listunsubscribe", params={"authtoken"=>"-------------------", "scope"=>"CampaignsAPI", "listkey"=>"------------------------", "contactinfo"=>"<xml><fl val='First Name'>best</fl><fl val='Last Name'>test</fl><fl val='Contact Email'> best@test.com</fl></xml>"}, headers={"User-Agent"=>"Faraday v0.11.0"}, body=nil, options=#<Faraday::RequestOptions (empty)>>

Response:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<code>IAMError%3AZ101%3AISCSCOPE_MISMATCH</code>

<status>error</status>

</response>