Subscriber's name is not changing - subscriberAddWithCustomFields


I have recently set up a custom form in our company's website which is used to collect some data and add a subscriber using only a part of it (form action="our-page"). I am using campaignmonitor-php-1.4.4, downloaded from

When a customer fills the form it gets recorded in our subscriber's list as expected, but if same customer decides to unsubscribe and then resubscribe his name is not changed when custom fields are.

$cm = new CampaignMonitor( $api_key, $client_id, $campaign_id, $list_id );
$data = $cm->subscriberAddWithCustomFields($_POST['email'], $_POST['firstname'] . ' ' . $_POST['lastname'], $fields, $list_id, true);

Any ideas?
Thanks in advance!

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