Work with X3 using PHP. I am able to create a customer account but when I try to read or modify I receive a 'No Such Operation 'read'' error message

The code I am using is below:

$keys = array();
$keys[0] = array("key" => "BPCNUM", "value" => $sageCustomer);

$results = $this->soapClient->read($this->getCallContext(), "BPC", $keys);

Can anybody help?