I'm getting the the following message on a chained adaptive payment call (via PHP). Can anyone see why?

```
array(5) {
  ["ACK"]=>
  string(7) "Failure"
  ["L_ERRORCODE0"]=>
  string(5) "81002"
  ["L_SHORTMESSAGE0"]=>
  string(18) "Unspecified Method"
  ["L_LONGMESSAGE0"]=>
  string(33) "Method Specified is not Supported"
  ["L_SEVERITYCODE0"]=>
  string(5) "Error"
}

```

Call is being made with PHP and the data is as follows:

```
METHOD=PAY&VERSION=84&PWD=xxxxxxxx&USER=support_api1.handmade.com&SIGNATURE=Ai1PaghZh5FmBLCxDCTQpwGx8jB26x4ALMef45mrA1XxMjpRjp20Iz6z.OBactionType=CREATE
¤cyCode=GBP
&returnUrl=http%3A%2F%2Fwww.handmadeandunique.com%2Fsuccess.php
&cancelUrl=http%3A%2F%2Fwww.handmadeandunique.com%2Ffail.html
&feesPayer=PRIMARYRECEIVER
&memo=Test+transaction
&trackingId=ZGP-32322323s
&ipnNotificationUrl=http%3A%2F%2Fwww.handmade.com%2FIPN.php
&receiverList.receiver(0).email=jennie%40xxxxx.me.uk
&receiverList.receiver(0).amount=100
&receiverList.receiver(0).invoiceId=ZGP-32322323s
&receiverList.receiver(0).primary=true
&receiverList.receiver(0).paymentType=GOODS
&receiverList.receiver(1).email=billy-browse%40hotmail.co.uk
&receiverList.receiver(1).amount=4
&receiverList.receiver(1).invoiceId=ZGP-32322323s
&receiverList.receiver(1).primary=false
&receiverList.receiver(1).paymentType=GOODS
&BUTTONSOURCE=PP-ECWizard

```