postback_url = null nas assinaturas

Estou tentando realizar uma integração com assinaturas. Nas transações normais ocorre tudo bem, mas na hora de fazer uma assinatura o postback_url sempre retorna null e consequentemente não tenho retorno em caso de alteração.

Tentei usando o sdk php v4 e diretamente com CURL, obtendo o mesmo resultado:

$subscription = $pagarme->subscriptions()->create([ 'plan_id' => $plano, 'postback_url' => 'http://duoapp.com.br/unitea_site/includes/ajax.php', 'payment_method' => 'credit_card', 'card_holder_name' => $cardHolderName, 'card_cvv' => $cardCvv, 'card_number' => $cardNumber, 'card_expiration_date' => $cardExpirationDate, 'async' => true, 'customer' => [ 'external_id' => $id, 'name' => $user['nome'], 'type' => 'individual', 'country' => 'br', 'documents' => [ [ 'type' => 'cpf', 'number' => $user['cpf'] ] ], 'phone_numbers' => [ '+55'.$user['telefone'] ], 'email' => $user['email'] ], 'billing' => [ 'name' => $user['nome'], 'address' => [ 'country' => 'br', 'street' => $address['endereco'], 'street_number' => $address['numero'], 'complementary' => $address['complemento'], 'state' => $address['estado'], 'city' => $address['cidade'], 'neighborhood' => $address['bairro'], 'zipcode' => $address['cep'] ] ], 'metadata' => [ 'id' => $id ] ]);

{"object":"subscription","plan":{"object":"plan","id":415045,"amount":111,"days":30,"name":"Doação Mensal - Tiago Centa","trial_days":0,"date_created":"2019-03-04T16:57:53.227Z","payment_methods":["boleto","credit_card"],"color":null,"charges":null,"installments":1,"invoice_reminder":null,"payment_deadline_charges_interval":1},"id":402047,"current_transaction":{"object":"transaction","status":"paid","refuse_reason":null,"status_reason":"acquirer","acquirer_response_code":"0000","acquirer_name":"pagarme","acquirer_id":"5c76f8063653a9ba424b6621","authorization_code":"835052","soft_descriptor":null,"tid":5944605,"nsu":5944605,"date_created":"2019-03-04T16:57:53.906Z","date_updated":"2019-03-04T16:57:54.430Z","amount":111,"authorized_amount":111,"paid_amount":111,"refunded_amount":0,"installments":1,"id":5944605,"cost":120,"card_holder_name":"tiago centa","card_last_digits":"4242","card_first_digits":"424242","card_brand":"visa","card_pin_mode":null,"card_magstripe_fallback":false,"postback_url":null,"payment_method":"credit_card","capture_method":"ecommerce","antifraud_score":null,"boleto_url":null,"boleto_barcode":null,"boleto_expiration_date":null,"referer":"api_key","ip":"191.252.135.250","subscription_id":402047,"metadata":{},"antifraud_metadata":{},"reference_key":null,"device":null,"local_transaction_id":null,"local_time":null,"fraud_covered":false,"order_id":null,"risk_level":"very_low","receipt_url":null,"payment":null,"addition":null,"discount":null},"postback_url":"http://duoapp.com.br/unitea_site/includes/ajax.php","payment_method":"credit_card","card_brand":"visa","card_last_digits":"4242","current_period_start":"2019-03-04T16:57:53.884Z","current_period_end":"2019-04-03T16:57:53.884Z","charges":0,"status":"paid","date_created":"2019-03-04T16:57:54.422Z","date_updated":"2019-03-04T16:57:54.422Z","phone":null,"address":null,"customer":{"object":"customer","id":1873460,"external_id":"216","type":"individual","country":"br","document_number":null,"document_type":"cpf","name":"Tiago Centa","email":"tiagomaker@hotmail.com","phone_numbers":["+555496594041"],"born_at":null,"birthday":null,"gender":null,"date_created":"2019-03-04T16:57:53.860Z","documents":[{"object":"document","id":"doc_cjsul8fke0afb6h6e08dmeaej","type":"cpf","number":"02194027017"}]},"card":{"object":"card","id":"card_cjsul8fl10afc6h6e1qj1ugv0","date_created":"2019-03-04T16:57:53.894Z","date_updated":"2019-03-04T16:57:54.416Z","brand":"visa","holder_name":"tiago centa","first_digits":"424242","last_digits":"4242","country":"UNITED STATES","fingerprint":"cj7t2pcew03tn0l09n98ibta0","valid":true,"expiration_date":"1020"},"metadata":null,"settled_charges":null,"manage_url":"https://pagar.me/customers/

pagarme / pagarme-php

postback_url = null nas assinaturas #323